Can't agree. The panels must vary. I had the 55UT50 for two weeks and was getting a good bit of image retention from game HUDs, ESPN and CNN logos etc. I had adjusted it with the WoW disc, had it on custom with contrast on 78 I think--so it wasn't on torch mode or anything. And I ran the break-in slides for 100 hours.
It was all temporary with the worst going away after 3-4 hours of watching other content. But I'd worry more if I was going to primarily use it for gaming and little else like the OP as he might not be mixing up content enough to wash out IR from games and could get stuck with some really stubborn IR.
I ended up returning mine, primarily for the buzz and my room being a little too bright for the UT50--but the IR annoyances did factor in. I'm not a videophile at all really--I just avoid junk brands and use a calibration disc. Other than that I'm not all picky about PQ and getting as close to reference as possible. As long as the picture is clear and the colors, skin tones etc. look ok to me I'm good to go. So I'm a lot happier with the Panny 55ET50 LED I got in exchange as the pic still looks great to me (dark scenes and motion aren't as good as the UT50 in a dark room, but I can live with that) as I get no buzz, can watch it with the blinds open and don't have to give any thought to IR. So I can go back to leaving it on ESPN for hours and not seeing the logo on bright scenes in other content for a few hours afterward like on the UT50.
Who knows. Maybe my set was just defective and got IR too easy. But I've tried plasma twice (a Vizio a few years back when on a tighter budget and the UT50) and ended up returning both due to buzzing (I think I'm just extra sensitive to hearing it and being annoyed buy it) and IR issues. So they're just not for me. Hopefully some day there will be new tech that brings the best of plasma without out the proclivity for buzzing and IR. Until then I'll stick with LED/LCD as being worry free in how I use my TV is more important to me than black levels, motion blur etc. Though I know that's heretical on a site dedicated to A/V enthusiasts.
In any case, I'd go LCD/LED for a primary gaming TV. If you don't need 3D (and not much use for gaming as so few games are in 3D), plenty of 47-50" options in the $700 range.