I believe all of the lag problems with samsungs are on 480i. The video processing and audio do not sync up. To the best of my knowledge, this is a problem with all samsung dlp's (not positive about the newest generation though). I looked at one of these sets until I heard about the lag issues, and then I pushed myself up to a Mitsubishi set (which is awesome). If I were you, I would avoid samsung and try to find either a Mitsubishi or Toshiba set, as all of them I have seen have been amazing and have gotten rave reviews. If you stick with samsung, watch out for the lag on 480i material (especially older gaming systems like NES, Sega, etc).
Edit: It is not the sound that lags, it's the video. The video processing takes too long so the video is delayed slightly from the sound. This is a major problem with timing in older video games as the image the appears on the screen is a split second late, so the timing is nearly impossible.