I'm with Nina on this I take out extended warranty on my large electrical products washing machine, tumble dryer, fridge freezer and TV.
On those items it's been worth it I've had new replacement items when things have broken down and the repair couldn't be done.
I stopped taking them out on microwaves as you can buy them cheap enough now but I did end up with 2 microwaves because the repair man couldn't fix it so I got a new one and it turned out there was nothing wrong with the old one.
I took warranty out on my computer, which is a desktop so that's covered until 2011 and that is on-site repair or replace.
I've always had good service from the cover I've had on my appliances and they are usually here within 48 hours to do any fixes.
So in my opinion there are certain cases where it is worth doing, but that's me