Well, I'm not much help in this department given that I've not had much interaction with the customer service department but from the minimal experience I do have, these are my conclusions:
1. The hardware and the engineering is top notch. Unless you are really unlucky, you won't have to get into all that customer servicing anyway.
2. Till date, my notebook has had three problems: the SuperDrive started making noise, the batter swelled up and, very recently, the buttom casing loosed up a little in certain places. The SuperDrive was replaced within a week, I got a new battery in five days (after it was out of warranty) and it is performing much better than the previous one. As for the bottom casing issue, they've told me that Apple is not shipping parts for some reason right now if the issue is non-critical and they have several backorders. They've returned my notebook to me and have asked me to return whenever I want after one month and they'll replace the whole case.
3. The SuperDrive and battery I got were brand new. No doubt about that.
4. The reps are helpful and patient.
5. The phone support is friggin' mind-blowing. They're very gentle and don't treat you like a newbie. I hated it when I called HP customer support once for Yash
bhaiya's notebook and he was asking me questions like, "Are you sure you have Windows XP, sir?" "Yes, I am." "Sir, it might be Windows 98. They look the same." No, they don't and dude, I'm using the computer – I know which OS it is running. Sheesh!
6. Did I mention that the hardware is awesome in the first place?
7. In my 1.5 years of owning this notebook, I've been apart from it for ten days. That's all. And all the problems I've had have been after the one year warranty ran out (but I do have AppleCare Protection Plan).
Personally, I think they have top notch customer service.
An important addendum: Since Apple takes care of the whole monty, the hardware, software and all that comes in between, their toll free number is a one stop solution for all your problems. You just can't beat that when compared to all the other vendors. There is no red-tapism and no throwing the blame around. If your machine has a problem of any kind, it's Apple's fault and they take full responsibility for it. Kudos to them.