Dev for, maybe, but my favorite part is how easy it is to hack. Actually, its not even hacking. The OS is open source, meaning Sony doesn't give much of a crap. You can get Ubuntu Linux on there in an hour or 2. For those that don't know, Linux is an alternate operating system to Windows and Mac OSX. It has multiple versions, or distributions, Ubuntu being one of a couple hundred, and the best, in my opinion. My current project is to get Ubuntu on my PS3 and then run Windows games on it through a program called Wine.
Heres how to do it with Spore. If you want to get Linux on your PS3, check the PSUbuntu forums.