Just thought I'd post that the ride went well and the advice you guys gave was helpful. There were somewhere between 1850 and 2000 riders (biggest jersey number I saw was 1850, and they limited it to 2000). Really nice ride, nice roads, lots of police. Even had my own police escort car for about 5 miles when I was bridging up to a group ahead of me. They didn't like me drafting though.
Of the people who ride the whole 100 (alot took the 50 or 75 mile turnarounds), I was either the 16th or 18th to cross the line (depending if I believe the lady at the finish line or my buddy who finished a few places ahead of me). It took 4:41 to ride, and I think the leading group was around 12 minutes ahead (at least that was the time gap at 80 miles). I rode with them awhile, but couldn't hang and knew if I tried I'd be in bad trouble. Course was very hilly in the middle. There were 4 climbs between 12 and 15%, although they weren't all that long, it sucked because they were all after the 60 mile mark.
Learned the following things:
Riding 30 miles without water is a bad, bad idea. Missed one aid station somewhere and got stuck out from the 50 to 80 miles mark without water.
Riding at the back of a long line sucks. Early on I was at the back of about 50 people, and the accordian effect was bad. Found it easier to just ride to the front and pull, then drop into a spot towards the front. Eventually though, like someone here said, it got down to small groups.
Gels really, really work. After I got some water at the 80 mile mark I rode awhile, and felt a little better, but was still feeling tired. I took 2 gels and within maybe 10 minutes I went from riding 18 to being back to 23 on the flats. Was able to pick up a coulple guys who took the 75 mile route and fly to the end. Without the gels, I probably finish 10 minutes later.