Do you have alot of HDTV broadcasts in your area? I know where I live NBC broadcasts HDTV, but thats it. Id personally hold off on an HDTV tuner until HDTV becomes more widely used, then you will reap more benefits AND it will be alot cheaper. I saw an HDTV card for a PC for $400. Not worth it yet.
Hauppauge makes solid capture cards from what I have heard, with good support.
Im still using my ATI All in Wonder, but once I upgrade my video card Ill be buying a seperate capture card, and from what Ive read on the boards here, Hauppauge is a good choice.