Velocity Atlanta is unique to Atlanta; there are no others. It's for Grady Hospital. Their goal is to be the "Peachtree Road Race" of cycling events with thousands of participants. I did it last year. While there were some first-year-growing-pains overall it was a good ride. They hire a large, well known cycling promotions company to handle the organizing and day-of logistics of the ride, which may give it more of a "polished" feel than some local charity rides.
Interesting! If it has Trish's approval it might be worth trying.