Trust me, Apple Stores are just as hit or miss as anyone else. Apple hires people based on personality, not technical skill. They literally have a section in their handbook for service providers saying how you can teach technical skills to anyone, but a desire to interact with customers is next to impossible.
Which is true to some extent, but you can really only go so far when it comes to teaching people technical skills. You can teach someone how to replace a HDD or something like that, but you can't teach the intuition a good tech has which helps them correctly identify problems. Sometimes diagnostic programs are wrong. I had a system once, all the diagnostic programs said there was absolutely nothing wrong with it, but the thing kept locking up and other weird things. Turned out one of the logic board memory banks was bad. Strangely enough, the system could pass multiple memory checks, but if you took the RAM module out of a particular slot and moved it somewhere else, the system started working perfectly.
Apple's TSPS (tech support for certified techs) was convinced it was the RAM itself, and I disagreed. I was right, though I give them credit for giving me the idea to test the memory banks.
That's the sort of thing you can't teach a person, you either have it or you don't. Anyone can be taught how to repair a system, but diagnosing a problem is an altogether different scenario.
And I've been to that Valley Fair store, and it's a right PITA to get to. Might not be so bad lugging a laptop in there, but pity the person who has to lug a 27" iMac in. The Oakridge mall a few miles away in San Jose's Blossom Hill neighborhood is generally much better. It's quite a bit smaller, but the important bit is there's a door to the parking lot right around the corner. And it's kind of the *** end of the parking lot no one tends to want to park in, so you have a better chance of finding a place.
But long story short... Apple Stores are hit or miss as to whether or not the job will be done well, same as any other place. Honestly, I'd rather take my system to an AASP, since they are in it for the money, and with Apple eating their lunch, they will absolutely be customer focused.
I'll even help out on that front. I have personal experience with two Bay Area AASPs. One is called DT&T, and I do NOT recommend them in any way, shape, or form. Horrible company, and they're up in Fremont anyway. Another place is called Compu Pro in San Jose, and they do good work. I've run across a few systems they've worked on before, and been fooled into thinking the systems had never been worked on before, which is about as high a praise as you can get as a hardware tech. Granted in one case they forgot to transfer the airport card when they replaced a display on a 13" MacBook Pro, but they do some beautiful work.
And the way Apple's labor reimbursement system works, is it's on a sliding scale. You make more money if you fix the system quickly, with as few parts as possible, and it stays fixed for at least 30 days. As opposed to a flat rate fee almost every other company pays out.
I work as an Apple repair tech, so I know what I'm talking about. But I don't, nor have I ever, worked for Apple, or either of the companies I mentioned. I've so far been very unimpressed with Apple's retail stores. The only time I've found them useful was when I needed them to drill out a screw for me. Apple just LOVES their tiny little screws that are machined out of this really soft metal and have shallow groves for the screwdriver bit, so the slightest of slips and the entire screw is stripped. The MacBook Air is horrible... There's 13 of these PH000 screws in the display hinge you need to remove to get the thing off. It's not fun if any of them strip. But just working at an Apple store doesn't magically mean that this will never happen. There have been some horror stories about Apple stores same as anywhere else.