I've always gotten comped stuff: Backlight went out, they replaced the keyboard part of the case (dents), iSight went out, they replaced a lot of worn keys, iPod was broken, it was replaced free. I'm a plain-looking dude with old equipment, I highly doubt the amount of effort put forth for my sake was to impress me personally.
Quote from your link: "doesn't that say something about the quality of your products"
I would say it the other way around, they got snippy so I got snippy.
I do think there is a relationship between how over worked the are, and how friendly they are. The Regent's St. store in London is mobbed whenever it's open, hence the poor treatment. The other store I've been to is in Stamford, CT. where my interactions have been much better - not as good as yours with getting comps, but certainly I left feeling happy.
This is too bad really, as the Regent's store is more of a flagship store, and that's where things should really be working.
I've had much better luck taking my computers to an indie Apple certified shop in town. I can drop the computer off with the friendly receptionist and go back to work, and their tech calls me back later to tell me what's wrong and get me to authorize a repair. Then I go and pick it up without having to wander through a shopping mall. Warranty work gets billed back to Apple so I don't pay. The service has typically been better, it keeps money in my community, and best of all I don't have to make an "appointment" only to still have to wait around 15-30 minutes. Everyone wins.
Something about the Genius Bar concept rubs me the wrong way. They really seem to try too hard to be that hip friend of yours who "knows computers." Maybe that helps take the edge off the experience for some people, but I'm not there to stand around and make friends, I'm there to get my stuff fixed with as little trouble on my part as is possible.
The Apple store in Philly just opened recently and they've been wonderful so far. Ex.: A few weeks ago I spilled water on my iPhone, rendering it unusable in important respects. I went to the genius bar (unscheduled), told the genius guy I spilled water on it. He was a bit surprised, said that no one ever admits to doing that, and gave me a new phone, for free.
iPhones and iPods have LCI (liquid contact indicators) built into them. It's a little white spot that turns red if exposed to moisture. Often, the LCI can be triggered for all sorts of reasons (not just dropping your phone in a puddle either, think a few drops of rain etc.)
People tend to get very hostile when there's some problem with their iPhone and get denied service due to the LCI being triggered, even if that isn't the root cause of the current problem. Hence the genius guy's surprise and over-generous response.
I dropped my iPhone on cement and it died. Took it in and told the guy I dropped it. He responded with "what? I didn't catch that, did you say it just stopped working? That must be what you said." and then gave me a new phone for free.
Since the front-line genius bar employees have so much discretion to go beyond the minimum required, it's really worth treating them well.
Showing up on-time for your appointment, not being a pain if they have a backlog and you have to wait a few minutes, having everything backed up if possible first, and being consistent and clear in describing what the problem is (at whatever level you know -- you don't need to actually know what the problem is, but describe the symptoms) -- will probably go a long way to getting a better than expected result.
My 3,1 MBP fan broke while I was in Iraq, and I bought a new i7 MBP to replace it. When I brought the 3,1 MBP in the day after AppleCare expired, they were great, and basically replaced the entire system, incidentally fixing cosmetic case, keyboard, etc. damage.
They've been equally good every other time I've gone in with a problem. They also have a great program for business users which gets you expedited service.
My only complaint with the AppleCare service model is that it's not so great outside the USA.
It is retail and it is customer support. The minimum standard for acceptable human interaction is several sigma above observed behavior, unfortunately.
Quote from your link: "doesn't that say something about the quality of your products"
You were snippy, they got snippy.