Newer/better plasmas are not nearly as susceptible to burn-in as the older/cheapers ones are. I do the vast majority of my gaming. as well as some web surfing, on one of
these and I have not seen even the slightest bit of image-retention, let alone burn in. Heck, I even left the thing on accidently all night with the computer off which left it with a black 4:3 screen with grey bars on either side; when I found it like that I immediately opened a all white webpage to check for burn in and there was none to be found.
As for resolution, obviously higher never hurts, but I am pleased with the image quality of this 852x480 screen running 1280x720; and this is coming from a guy who always shoots for 1600x1200 on his 21" trinitron. The scaling abilities on the screen is quite good so 720p in 3d games looks quite a bit better than 480p, though 1080p doesn't show much difference from 720p. I'd imagine that an HD plasma would show the same benefit between 720p and 1080p.