I don't play games on the phone at all no fun gaming on a tiny screen, I only installed sudoku for playing once in a while.
Have seen 2 or 3 crashes inside whatsapp (sometimes it takes long to load, sometimes it just hangs itself), but hey thats whatsapp at fault who don't give rats a** to updating their program to work smoothly with WP8. WP8 as an OS, is smoother than the smoothest chocolate you've ever eaten which melts in your mouth.
I have a nasty habit of exiting every app before I start another, the max no. of apps running would be 2 (if I have to multi task), the same applied for android too (But then I couldn't control the background apps which led to hangs and crashes like a mad kid terrorizing the house for not receiving his favorite candy for lunch).