Working 2 minutes from Apples Regent Street (London) store and having had a few problems with my MacBook I can say that Apple is no better than any of the other retailers if not worse.
You'll need to get yourself an appointment first. No problem if you paid the extra 200 pounds for pro care; you can book up to 14 days in advance. If you're sane however, you can only make bookings for the same day on their website. I stayed awake til midnight a couple of times before I got fed up and realized that there's absolutely no point in trying.
I thought the idea was at some point: Walk into the store, make an appointment, come back later; but that's definitely not the case.
I used to have a dreadful Dell notebook, and while the thing itself was rubbish, the service was a lot better than what I experienced with Apple.