Quite frequent.
I was scaling a head on a character, it was scaling too fast as usual. (No obvious way to slow the scale increment down).
So I quickly duplicated the head, so when the scale throws off too fast, I could use the duplicated subtool visually to guage how far to scale down.
When I was done, I switched to the duplicate subtool, then hit delete.
CRASH
Not just any crash, I mean entire computer locked up tight had to hold down the power button to shut it all down.
Fantastic sculpting program, but no offense frustrating amount of very frequent crashes when using deformations, undos and deletes (the most basic operations).