it'll work, and it's cheap, that's about it.
the top dog right now in back to back test is the ati theater 550 card. Low profile, single tuner. Buy two if you want dual tuner functionality. It has a 3d comb filter which does an amazing job cleaning up composite signals (most set top boxes can output composite, or rgb, and tv tuners dont accept rgb as an input, so you have to downgrade to composite, which makes the theater 550 so attractive).
pvr500 is great, just make sure you get the "optional" expansion bracket/daughtercard so you get 2 composite and 2 svideo and 2 audio inputs so you can actually run two sources into it. As standard, this is generally not supplied.
Problem is...this htpc stuff is addictive, and you can spend hours staring at the tv tryng to correct every visual error you find...so starting out with a great tuner (for a few hundred R's more) is a wise decision.