N800 owner, here.

Worst case, in my experience, if your tablet won't boot, it will need a reflash. I actually mailed it off for repair one time, unnecessarily. I should have tried to flash it, myself. Newbie mistakes.

If you can't flash it, or flashing doesn't solve your problem, then you have a real problem that you probably can't handle yourself. They had to replace my touchscreen, on my first repair. That was a real issue. The second time, I was just gun-shy, if you know what I mean.

The lesson, in short, keep a current backup. If you install something, make a new backup. Don't overwrite your old back-up, either. I keep one "known good" backup, and one "just installed something new" backup. If my tablet crashes hard and good, I don't sweat it anymore.

I haven't had a problem since the first OS2008 beta, though, tbh. I had a couple OS2007 updates that were flaky as hell for me. I cussed. I cried. I posted diatribes. All water under the bridge now. I'm a happy camper with OS2008.