I've been seeing a few games offer it lately, although not many. I know Infamous 2 has it and I want to say Two World's 2 did but I'm not certain.
I have my brightness and contrast settings below 50 (out of 100). I knew image retention is always an issue with plasma type TV's when I purchased the TV. But the true 500hz refresh rate and much truer black's is what made me decide to get a plasma. Also the TV has built in anti image retention software it just doesn't work as well as I'd hoped. Also it's not really that much of an issue if I can force myself to take a good 30min break every hour or so, but that's especially difficult with an RPG game, the desire to continue looting and leveling is just too strong!
Its not so much the mini map I'm worried about. Mostly the character icon, available abilities, health and mana bar's that could be an issue.