My former roommate has one. Changed his life. His back pain is no longer chronic. Your best bet on a deal though, is to pit competing mattress stores against each other.
The beds are unbelievable and are definitely worth it. I've worked with the people at Tempur and had the chance to visit one of the North American plants - really cool how they make the stuff.
Tempur beds are the ONLY beds which I've EVER been able to sleep on my back and I always wake up feeling great. Worth the extra cash.