#5: i agree about riding solo - being tethered to someone else, who most likely won't want to ride the exact speed as you the whole time, can be a drag. riding with friends is fun, but keeping pace isn't easy.
this was my first year doing it solo, and i enjoyed the hell out of it! although i did paceline at 25 mph for the first 50 miles, for the rest of the route i went at 15-20 mph, and stopped about every 40 miles or so.
and riding at a medium pace, but stopping infrequently, meant that i would see a lot of "faster" riders again, and again, and again. had i been riding with a partner i probably would have had to stop more often.
some more points to add to the list:
#10: if you want to use a nice bathroom (that isn't a 100+ degree portapotty with a big line in front of it), just go to a convenience store or gas station. they mostly have air conditioning too.
#11: insulated water bottles are worth it! i had one of them, and it worked as i hoped it would. my other bottle's water would get hot after about 20 minutes in the sun.