US21 certainly is fast, compared to other boats of that size and vintage. It rates PHRF 201, 50 sec/mile faster than the SJ21 (252) and seventy faster than the Catalina 22 (270). It's a very quick little boat, with a clever interior layout.
SJ21 is popular in the Carolinas, since SJ had a second plant in NC. There's a fairly active fleet in the Lake Norman area.
San Juan 21 Fleet - Lake Norman Yacht Club
Blackbeard Sailing Club
The class will hold its 2013 NAs on Lake Murray, SC. You can buy one for under $2k in sailable shape; race ready for a bit over $3k. Under 2000# on the trailer, real easy to launch. Not sure how the boat got its reputation for tenderness (but I'm a dinghy sailor moving up, so it sure feels stiff to me.
) Goes nicely in light air; can be managed in heavy air under reefed main only.
Doesn't care for chop, tho. Not the boat I'd choose for Pamlico or the Atlantic. Cabin is tiny on the Mk1; slightly less cramped on the flush deck versions. We've lived on our Mk1 for twelve days, so it's a matter of what you consider 'accomodations.'