OK, I'm going to venture a guess here. Some of you still own HDTV's from before the NTSC analog broadcasts were turned off. In other words, you have sets with BOTH ATSC digital and NTSC analog tuners built in. In the days when both ATSC and NTSC broadcasts were happening, these sets switched between digital and analog tuning modes automaticly as you scanned the airwaves.
If that's the case, since the only over-the-air broadcasts remaining are ATSC digital broadcasts, you have NO REASON WHATSOEVER to need the overscan feature, it is a legacy feature left over from now-obsolete NTSC tuners.
Digital broadcasts do not make use of a "blanking interval" between fields or frames to contain other data. With digital broadcasting, the pixel values, the sync timing, the audio, the closed captioning, and everything else are just seperate data sets, multiplexed together for broadcast. There is no data physically adjacent to video signals, and overscan is not needed to conceal the artifacts on the edge of the video frame - because there are no such artifacts.
The NEXT HDTV you buy doesn't need an overscan feature.