I'd go for it. Here's the deal...if you can afford DLP or LCD rear projection or otherwise, get it because they are better and don't suffer burn in.
If you already have, or all you can afford is a rear projection CRT, get it anyway (try to make sure it supports 720p though). Just be careful about leaving static images on them.
I have a friend with a Mitsubishi Diamond series 65" with the ReplayTV pause symbol burned into the lower right of the screen because they paused a show and for some reason the screensaver never came on. They left it overnight for like 8 hours.

But if you're careful this won't happen to you.
A bigger concern for me for burn in, was the verticle bars you get on a widescreen TV when watching older 4:3 format TV shows or movies. I refuse to watch my TV "stretched" where everyone looks short and fat, but they say those bars are bad for TVs that suffer burn in. I guess now, they make them gray instead of black to try and help, but the manuals still recomend against watching material with bars on the sides.