Had my iMac for 3.5 years and loved it till it broke.
Apple store diagnosed video card failure and kept it for repair. 3-5 days they said.
After 5 days they asked if I would mind having a replacement machine instead because they werent happy with the repair work that had been done.
They said would you mind a 27 inch version because we dont do the 24 inch any more!
I collected the replacement - it was brand new with quad processor and 4 gig ram and a 1tb hard drive - all better than my origional, they said you had better have a wireless keyboard and mouse because your wired ones wont work with the new machine.
All free of charge.
Apple rocks.