Good post Cypress!
Need to add M35+:
Usually faster than the 3s, but slightly shorter distance (45-60 minute crits, 40-50 mile RRs). Lead by Cat 2s who don't feel like racing 106 miles on Saturday. Decent field sizes (in TX, >40). A lot of varying abilities here, but the guys who are 3s can generally keep up with the main field. The 4s have a tough time. You find a lot of guys who aren't that strong, but are VERY smart doing well. Tactics are near the P/1/2 level, with many team members having assignments and carrying them out. This is where guys like myself end up -- I'm strong enough to get upgrade points in the 3s, but have no desire to race 106 miles on Saturday as a Cat 2.
M35+ is like a fantasy bike racing camp -- feels like the pros, but it's accessible.