I would wait. It is getting terrible TERRIBLE reviews and a lot of flack for this whole rental thing.
Just wait. The price will drop, they will fix this problem, and release a patch allowing you to reinstall it.
I think the game might be a worthy play, but not 50 bucks for the communistic standpoint they are going with.
People are making way, way, way, way too big a deal about the DRM on Spore. And it's not getting terrible reviews. It's gotten reviews that are mostly positive if a little let down by the hype.
It's worth the money. It's fun. Don't worry about anything else.