As long as it's a true ATI (not just a "Powered by ATI" knock-off), I say go for it. I have one, and the S-vid out to TV couldn't be easier to set up. The true ATI's have full-screen, centered TV display right out of the box, unlike "most" (non-VIVO) of the nVidia GeForce cards.
The only con to any ATI card is if you also want to use the DAPHNE laserdisc emulator...unless you feel like editing source code and compiling your own, DAPHNE prefers nVidia cards. They did create a workaround for the problem in ATI's drivers, but from what I've heard they might not be enabling this in future releases.