I think you have to give the strech some time. My wife doesn't like it either, but it is becoming more tolerable over time. Before I decided on the XWX, I was researching STB's as well. Each of the three you cite (really 2 as the zenith and sony are the same) had tradeoffs to consider. There is a huge thread on this site about the Samsung that has more info than you will probably need. I seem to remeber that the Samsung doesn't have an expanded stretch mode which means is should perform similarly to the Hitachi's 16:9 standard mode. I think the sony/zenith has what most people think is a superior expanded stretch mode. You can read and nitpick for days about the Samsungs red push and other "design flaws" which they may or may not be fixing, the Sony/Zenith's lack of always-on s-video output, etc. etc. etc. If all you are concerned with is the stretch modes, you should go try to find somewhere that is demoing all of the boxes you are considering and see for yourself.
FWIW, I probably would have gone with the Samsung if I didn't get the built-in tuner. Also keep in mind that a couple more boxes are due out at the beginning of the year.