I chose Never but it actually froze up 2 times.

One while playing Quake III and had Skype, Pidgin Internet Messenger, E-Mail and Web opened. It didn't froze, it was just really laggy so i decided to remove the battery.

The other time was when i was playing FLAC musics and had multiple browser windows. It didn't completely froze up but, once again, i'm not too pacient.

Other than that, great phone! And of course, every phone freezes, for some reason or other...

...including iPhone, check iPhone 4 freezing - Google results

This is just to say that every phone has it's freezes and crashes.