Overall very good, when I needed it, which has only been four times.
When my PowerBook G3 would no longer charge from the plug, the Airborne Express dropped off a box, picked it up, and returned in in about 5 days.
When my PowerBook G4 (refurb) arrived DOA, the Apple Store at Sommerset (only one I had back then), I took it in without an appointment, and they had it back in about 4 days.
When my US-purchased iMac started suffering SMART errors while I was long-term in Canada, I was a little worried. They happily directed me to an authorized service center, and they replaced the hard drive then and there.
The last one is a little shaky, though. The service people were excellent, but the timing was horrible! My big iMac had a faulty video card. I took it to the Partridge Creek Apple Store (just up the road!), and for some reason it took a f’ing month for them to realize that they couldn’t fix it and get me a replacement machine (under Applecare, and the replacement machine was a significant upgrade!). It went like this: remove the video card, send it to Apple, wait for a new one to arrive, realize it wasn’t the only faulty thing, remove the motherboard, send it, wait for a replacement, call me to pick it up, thing is in worse shape, repeat the whole process, and then send in the bad Mac and wait for a new one. Yeah, it pissed me off having to be stuck with the 17" Mac the entire time.
I think I’ll never, ever go to the Apple Store again for a repair. The fact that they don’t keep parts in stock sucks bad enough; the fact that the depot has to wait for the “bad” part to arrive before sending a good part back to the store is simply insupportable. NEVER AGAIN.