I would say it REALLY depends on the handset... I don't know how Nokia's maintenance/repair with Symbian devices goes, but it's probably really good. They obviously won the following of a decent amount of people for a while. However, the N900... not so much. I've heard some people get their devices repaired/replaced within a week, some have their N900 languishing for weeks - in rare cases months - so it's very, very much a matter of luck.

However, I have never personally have had anything that required Nokia involvement. And personally I think people sometimes turn way too quickly towards 'hey let's send this thing off to the official care centers' whenever something goes wrong. Every single problem I've ever had, could be fixed with a reflash. It's only when you have hardware issues that you need to send it off, or you've screwed up the bootloader, or something that serious... At least, such would be my guess.

Ultimately, I am going off what I've read on this forum, and my memory may be off.