I've gamed on a little Barco 708s for years now. No overscan issues (you can tweak these to death, anyway). As for maintenance -- get a solid unit, set it up right, and you barely have to touch the thing. I've only had to swap out a splitter so far on my setup. Very simple, and I'm not even a technical person.
No burn-in. Just use common sense. Keep the contrast reasonable (as you mentioned), blacken the room, and keep the static stuff offscreen as much as possible. You'll get years out of it. Tubes can last a really long time. Heck, I go to 50-60% contrast a lot and it's still vibrant. Wouldn't recommend a full PC setup on a PJ, though, for various reasons.
Yeah, you certainly want to avoid any extra processing to avoid lag if you can. My 708 takes 480p component directly -- instant response, and I think it looks great at ~100"+. Everything from Wii to PC stuff is a real visual blast. I mean it! I save 720p/1080i for movies and HD games.
Side note... a lot of folks seem to dismiss black levels for gaming, but they make the adventure / RPG / action stuff so much more intense and cinematic. It's simply a treat playing stuff like Metroid, Zelda, Resident Evil (or anything else, really) on a huge CRT PJ screen.
Hope I'm not saying stuff you already know...!