I would say that compared to PDAs the N800 is good. It's far more scary when my T3 has a 'fatal reset' than anything that's happened on the N800 so far. The only times I've been worried was when it didn't want to boot, which for me was fixed by temporarily removing the internal SD card (and this problem is gone, for some reason), and a couple of days ago when it stopped in the boot process because of an upgrade to a buggy application (which was also resolved speedily). (In any case I quickly realized there's almost never any reason to ever turn it off. Was forced to once when the email app didn't want to start, but other than that I've only had to reboot because I was experimenting with the 3party Kismet application, which most certainly can't be blamed on the N800.)

No other serious problems (that is, problems that actually affected me, unlike when the PDA loses all its information and the like). Compared to a stable desktop computer the N800 is probably beta, compared to PDAs it's gamma.. PDAs are all beta, at best!