I considered joining Riverside for the summer. For $600 for four months it seemed like a reasonable deal, given that it has decent facilities which include a couple of well-maintained indoor tennis courts. Unfortunately, though, these courts have an odd surface that I've never seen anywhere else. I can only describe it as 'soft and mushy'. It wasn't bad to play on, and was probably easy on the body (much of the clientele appears to be of an older demographic here, and maybe the choice of the surface was made for their benefit), but I assume that playing here often would make it hard to adjust to typical hardcourt surfaces, where the ball bounces harder, faster, and higher. I'll continue looking for a place to play tennis this summer...
As for the other facilities (gym, pool, etc), they're all decent, but I've seen better elsewhere in town. The star attraction here is the tennis courts; it's unfortunate they're so strange...