I have a 24 inch 1920x1200 monitor. I tried to use it for gaming for a while, but sitting in a chair playing console game is bleh (plus the extra vertical resolution created an annoying vertical stretch).
You use a plasma monitor?
I saw a cheap LCD once that suffered some kind of image retention. However, it eventually went away (it was an LCD where I work). It had DOS style words from one of the boot screens issued by the BIOS that got stuck one day and sat there for a really long time. Using windows regularly for a while made it go away.
But generally LCD's are considered invincible against burn in.