Mark, I took over the lead of the Y2K project for my company (large Oregon firm) when one of my peers left to be a consultant (read, big money). I had well over a hundred people on my team, and thankfully almost all were highly competent. My co project manager (she was the secret of my success) and I took an effort that was purported to be a death march, and turned it into a program that turned out to be not only highly successful, but fun for the team. All of our systems handled the dates appropriately, with only one that gave us performance issues. That issue was caused by recursive date checks in historic records (sometimes C++ really sucks), and was cured when we removed that business requirement.
In my entire IT career, I found that effort to be the most productive. Now if we could just nail down a single time period.