I just made the switch myself, and I can tell you that I'll never go back. Blu-rays and free online are nice, but they wouldn't make me give a shit.
No, the reason I switched and the reason I'll never switch back is the reason anyone should choose a console: The games. PS3-Exclusive games are more right for me than XBOX-exclusive ones. I'll never say they're better, because what does that mean?
but with Xbox you have stuff like Left 4 Dead, Halo, Fable, (Also Alan Wake, which almost made me go back, but no. Doubt is Death) stuff that I've tried and it's simply not for me.
PS3, on the other hand, has the developers of my two favorite game series ever (Sly Cooper and Jak & Daxter) on the friggin' payroll. Then there' inFamous, Flower, and Blu-rays again.
That said, as you may already know or will soon find out, Outside of the actual "Game" part of the equation, the 360 is better in almost every way. The store works better, Online play works better, finding new demos works better, knowing about 'what's new!' works better, the whole interface just makes more sense.
There is a certain kind of game that gets made for the XBox, and I do not want that kind of game. I want inFamous. And I will pay more up front for the privilege of being entertained in this way. Enjoy. And buy inFamous.
Also, when it comes out, buy the Sly HD collection. From a purely academic standpoint, these games do an incredible job of covering how gaming evolved on the PS2.