I would not buy a plasma to use exclusively as a gaming monitor, especially for PC.
Image retention/burn in problems while not anywhere near as bad as they were years ago, still exist and would become more of a problem with static images in gaming and with Windows desktop.
Parents have a 55ST50, and it's tied to a desktop, no image retention on it. It's used for Netflix and general desktop display duties.
Actually that's not true, it did get the Netflix pause screen toasted into it once. So I popped it into Vivid mode, and ran the scrolling bars. Image retention went poof.
Of course this requires that you do actually do a break in of the plasma when it's new, watching anime, movies, etc. for the first week while restricting it's idle screen time. Of course calibrating before and after is a must.
I know JZL has been rocking a Panny plasma as his gaming screen for a few years, and loves it. He plays a flight sims, UT, etc.
Of course it can also depend if you have a proper noise filtering power bar/UPS sitting between the wall and the screen, and other factors. I do know though, running a Plasma at full burn, leaving a static menu on it for 16 hours a day, weeks straight will create a difficult to remove ghost. Though even then, running full screen looping material, with the scrolling bars a few times, removed it.
As for the windows desktop, setting your taskbar to autohide, restricting the number of icons on screen, not using a solid colour backround, using a full screen backround image, and using a screen saver/screen off feature.