GBW,
I'm new here and am happy to have the opportunity to contribute some info regarding my experience with a 2002 F350 SRW longbed crewcab diesel 4WD w/ auto transmission.
Fuel mileage: anything you want it to be, ranging between 21 mpg and 14 when empty. Varies directly with speed, headwinds, A/C usage, tire size, modifications,and topography. When I drive back roads between Raleigh, NC (elevation 300') and the Chesapeake Bay (a dead flat 200 miles), if I observe the 55 mph speed limit, refrain from fast starts and lots of passing, don't use the A/C (when the season allows), and generally handle it like there's an egg beneath the skinny pedal, I can get an honest 21 mpg. She turns around 1500 rpm w/ 3.73 gears in overdrive with the torque converter locked. With the 12" x 33" Nitto A/Ts she's shod with now, a fairly heavy fiberglass shell, and a whole bunch of fishing and camping gear, running the A/C virtually the whole trip, and running 72-74 mph from NC to Nevada, Idaho, Montana, Utah, Colorado, and back to NC in July, I recorded 17.1 mpg for the trip. Yes, it's difficult to drive that slow when the posted limit is 75. That said, it's pretty cool to run 80-85 mph on Michelin LTX M/S rubber and still get 15 mpg.
F350 vs. F250: As I understand it, my 350 is exactly the same truck, in every single sense, as an 02 F250 excepting this: There are 2" blocks over the rear axle (to allow more squat when loaded?) and it was equipped with Load Range E tires from the factory. It's a 9,900 lb GVWR, though, and I THINK that corresponds to a 250, anyway. Bottom line is until you go to a dually, there's not a real difference between 250 and 350 in a SRW. Mine has the "camper option, trailering option, and off-road option", which to the best of my knowledge gave me small additional rear helper springs, an RV style trailer light harness, and sway bars front and rear. Maybe only a 350 can get all of that in SRW configuration, I don't really know.
Diesel vs gas, winter use and maintenance: I bought my 350 used with 96,500 miles in May 2004, mere hours, it seems, before diesel suddenly became more expensive than gasoline, a condition which has persisted all but a month or two since then. Go figure. I change my own oil, oil filter, clean my K&N air filter, and change my own fuel filter. I'd used Rotalla 15W-40 until December 2010, when I switched to Rotella T6 5W-40 full synthetic in preparation for a trip to Utah when I'd be at 7,700' nightly for 10 days in early January, plus leaving it at the ski mountains, generally at 8-9,000' all day, with no block heater plug ins during the day. We had a number of mornings in the single digits and several days when it never got > 10-14 deg at the ski mountain, and she fired right up every time (I was able to plug her in where we stayed, but I could have gotten by without doing so). My oil filters run between $10-17, the Rotella synthetic is now $24-26/gallon at WalMart (I need 14 qts to change), and the fuel filters run around $20. She gets an oil change at between 5 and 7,000 miles, a fuel filter between 12-15,000, and I clean the K&N before any long trip and right after our Springtime pine pollen season back east. I send off a sample of the motor oil to Blackstone Labs annually and also the ATF at every change (which is at between 25-30,000 miles). The lab report guys rave about how good my motor oil and ATF numbers are, so my filtration remains good and my change intervals are fine.
Diesel vs gas, operations: There is no comparison. Since my truck is no longer my daily driver and is strictly a FunMobile, my entire focus is moving heavy loads (24' boat; tandem-axle car hauler, full bed-load of FunGear, etc) and having wholly thrashed lots of half-ton gas pickups and Suburbans over the last 35 years, this first diesel had me saying "why did I wait so long?" from the beginning and every day in between (been 7.5 years now with the 350). Even heavily loaded or towing, if I want to or need to, I can accelerate uphill, something I could only dream of with a gasser bursting at the seams. I literally never feel as though I'm abusing my truck.
7.3 vs other Ford diesels vs other makes: At the time, in 2004, money limitations limited my options to 2 to 3 model years prior, so 01 or 02 was all I could afford. I required a full crew cab, as my "extended cab" Chevy half-ton predecessor turned out to be a torture chamber for those I was annoyed with and placed in the back. If I recall correctly, in 02 and definitely in 01, Ford was the only one offering full crewcab diesel longbeds, with Dodge and Chevy only offering extended cabs. Either way, I was carrying a grudge with Chevy over their automatic transmissions I'd exploded so many of, and the Dodge 12 valve Cummins seemed like a great engine surrounded by a not-so-great truck. I have an affliction called "IH Scout-itis" and came from a trucking family background where my family's company ran all IH equipment, so the Navistar International provenance of the 7.3 was very appealing, and it still is. As to the 6.0 and 6.4 Fords from 04 on up, what EVERY SINGLE GUY I've spoken to since 2004 has said is "man, I wish I had my 7.3 back". That tells me a whole lot.
Problems with trucks like mine: Ford made the front wheel bearings and spindle bearings a non-servicable unit. They tend to die fairly young: both of mine had to be replaced by around 160,000 miles. Replacement cost is around $700 EACH SIDE. The auto lock front hubs are plastic junk and the vacume hoses dry up and crack early and often. Once mine did, and since the incredibly flimsy plastic manual locking mechanism was very difficult to turn and eventually got brittle and broke, I replaced the OEM junk with Warn Premium manual locking hubs, so now I have to stop and lock in, the way a proper man should, anyway. The front leaf springs were completely worn out by 175,000 mi, as were all of their bushings, the tie rod ends, and the front sway bar ends. All were replaced with a "leveling kit" from Four Wheel Parts Wholesalers (new leaf springs and all hardware). I guess supporting 1,200 lbs of glowing diesel is tough on front suspension parts. The real weak link is said to be the 4r100 automatic trans. There's little point in looking for a used diesel pickup w/ a manual transmission here in the east, as they pretty much don't exist. Apparently the weak link within the 4r100 is the stock torque converter, and when the tc grenades, the whole trans is destroyed. The rebuild is generally around $4,000. But, here sits mine with 218,000 miles as of today, and the trans has never been gone in to. I change the ATF religiously, as did the first owner, I run top quality synthetic ATF and have a Magnefine in-line filter in addition to the internal filter, which I've also changed 3 times since purchasing the truck. Even though I tow heavy, I don't tow a great deal, and I'm very light on the skinny pedal when I do. My own opinion is the guys who blow up their 4r100s are those who chip them up and then run the piss out of them, and I wonder why they're surprised when the transmission overheats and cooks. Oh, mine has the stock tune--no aftermarket chip, etc.
Overall quality and dependability: I've run 4WD trucks on a full time basis since 1973 when I got my first IH Scout while at Appalachian State University in the Blue Ridge Mountains of NC. This Ford is only the second Ford I've had in the this 35 years, and it's hands-down the best truck I've ever had. No F150, K1500, half-ton Suburban, Scout II, Jeep Wagoneer (fullsize), fullsize GMC Jimmy, or IH fullsize pickup I've ever owned or run could so much as hold a candle to this F350. Given the 218,000 miles, the thousands of dollars spent on replacing "wear parts", while painful, seems normal. I replaced the OEM water pump, tensioner assembly, and idler pulley at 207,000, at which point the pump was screeching like an owl under the hood. So, lots of wear parts, but not a single thing has "broken down", nada, nothing, zilch, for nearly 125,000 miles over the last 7.5 years.
I plan and hope to keep my F350 for at least 5-6 more years, where my current "twice a year" runs out West and some beach + Blue Ridge weekenders will add up to 14,000-18,000 miles/year. I am currently rustling up the $$ for a lightweight popup camper and plotting to spend a week in Elko County, NV in 2012. Even though the fuel cost (vs gasoline) deal sucks, with less to maintain and repair, and with decent mpg, I'm probably still ahead on a cents per mile calculation. Even if I could, I wouldn't turn back the clock and get a 3/4 or 1-ton gasser.
Hope this helps.
Foy in NC
and will report on them after I install them next week, can't wait. And to bitch about Ford I stopped by to get some new crush washers for the oil drain bolt and it was priced @ $10 
