a) Every Apple store has a dedicated small business contact. If you call the store, you can get to this person through the phone tree. They can make special arrangements for businesses, up to a point.
b) According to http://www.apple.com/support/products/mac.html, if you have AppleCare, you can request on-site or even mail-in service. I've used the mail-in service a half-dozen times over the years.
c) Even in a world filled with Apple Stores, there still are third-party retailers. A local shop (closest to me is http://tenplus.com) is likely to give you better service.
(As for the much-mentioned half-day of revenue, the store's also open on weekends)
Have you tried getting a genius bar appointment at the weekend in London? It's not easy. Also, it's still work if you're self employed, and your time has a value.
When I go to an Apple store, I ask for their business sales staff and I skip all the bubbly "Oh is this your first Mac?" blue shirts. Often I call ahead, and my hardware is waiting for me when I arrive.
When I have issues with hardware, I do not deal with the Genius bar, but as I do with all other PC companies, I talk to a business support person at Apple over the phone, and resolve most issues either on the phone, or via RMA. They sometimes schedule me an "appointment" of sorts at one of the local Apple stores, but I don't have to wait for anything. I drop off the machine, and come back and get it later. They have bent over backwards for me on multiple occasions, even allowing me to come pick up hardware after hours.
So yes, I think that Apple is especially good at small to medium sized business support. Better experiences than I've had with Dell and HP.
I had a standard MacBook - about 2 months old - when I noticed, whilst working on it on the train, after picking it up one of the screws from the underside had become loose and fallen out. I spent a while trying to screw it back in with my fingers on the train, just enough to stop it falling back out again.
When I got home I gave it a proper go with a screwdriver. Problem solved? Nope.
Over the next few weeks this kept happening - not just with that one screw but with about 3 or 4 (of the 8 in total). I got suspicious and took it straight to the Geniuses.
I've calculated the total time, per appointment, to be 2 hours - 10 minutes getting ready (shutting down, disconnecting displays and HDDs, etc), 40 minutes travel there, 15 minutes waiting, 15 minutes being served, 40 minutes travel back.
Appointment 1 (2 hours elapsed): Problem diagnosed, genius did the screwdrivering themselves.
Appointment 2 (4 hours elapsed): Screws still loose, genius took a look and put in an order for some new screws.
Appointment 3 (6 hours elapsed): Screws have arrived, genius replaces all the screws.
Appointment 4 (8 hours elapsed): Screws still coming loose. Genius 'resits' the MacBook underside.
Appointment 5 (10 hours elapsed): Still no luck. Genius orders new MacBook rubber base.
Appointment 6 (12 hours elapsed): New rubber base is fitted.
Appointment 7 (14 hours elapsed): Screws STILL coming loose. Genius orders replacement of base 'fitting unit'.
Appointment 8 (16 hours elapsed): Genius fits new base fitting unit. This takes 3 days so I can't use my MacBook at all during this time.
Appointment 9 (18 hours elapsed): Still no luck. Genius offers to replace MacBook. But, I don't have an entire system backup (I was using BackBlaze and had a hard drive crash the month before), so I have to fork out £80 for a HDD to set up Time Machine again.
Appointment 10 (20 hours elapsed): Backup taken. MacBook swapped.
Appointment 11 (22 hours elapsed): New MacBook doesn't boot properly. ANOTHER replacement...
... and finally I had a faultless MacBook again. All it took was almost an entire day of my life.
I emailed a copy of all my Genius Bar woes to email@example.com - nothing for 3 weeks, when one morning I awoke to a phone call from my local Apple Store. They said they'd heard about my troubles 'via Cupertino' and promised me if anything ever went wrong again, I'd get a full refund...!
I am surprised: Loaner policies, and ease of swapping to other apple computers (migration assistant works from time machine) makes Apple great for freelance in my opinion.
Also: Mail in service is far superior timewise than going someplace in person.