Well, clockworkmod completely borked my Tab (or more likely it's me who didn't do it well).
Thought clockworkmod was more foolproof - in the end, I only gave a restore command. After restoring the Tab couldn't wake up, only showing logo, and wasn't possible to boot into cwm by power-volume up.
Luckily I could recover the firmware with Odin and presently I'm in the process of restoring everything - or at least I hope so.
The Tab isn't much more reliable than the N900, in the end