What you need is a HDTV with a low response time, ideally you want something with less than 8... maybe even 6ms response time as a maximum.
I don't actually own a HDTV so I couldn't say for sure, but using the same logic for TFT/LCD monitors should see you fine with HDTV's as well. I have a 19" widescreen monitor with a 5ms response time and I've had absolutely zero problems with any games on this. The effect of lag that you mention is called Ghosting.
It won't actually be much of a problem at all, the only occasions where it could be is with rhythm games such as Guitar Hero, but even then they offer calibration methods to make up for screen lag given by HDTV's.
Again though, look for a screen with a low response time and you should be absolutely fine.
