The only crash I've had lately was the bunny level one, where it crashes every turn but game does an emergency save and you don't lose the character. It wasn't in my computer though, was at school. In fact, I can't remember when my last crash was at home, and that's using winbeta4 under windows.
However, I use to make backup saves because my old computer used to crash a lot (the computer, not adom) so I lost 90% characters that way and needed the backups. Now it's just a habit, have never needed to backup the file.