A consumer's perspective:
The shop that does my MB is clean but not at all posh; its advantage is an owner who's a very knowledgeable and experienced tech himself, very straightforward, honest and good. They flat-rate by the book on most things, but do make it right if they goof, and will accommodate an owner's reasonable preferences. Example--My 560SL burned oil after the first change they did, which was also the first I did for the then-new-to-me car; they'd used 10W30 (see manual for recommendations). I switched it over myself to 20-50 high-mileage-formula Valvoline. At the next change, I asked for the same oil I was using; they said "no problem", ordered it and did it.
My preferences--I don't need walnut and leather, but like a clean, well-kept shop with comfortable furniture that's not worn out. If you're choosing between upscale looks and a usable quiet room for me to do work while I wait, please give me the latter; a separate "quiet waiting room" is extremely helpful, and access to power so I can use my laptop while waiting is too. Coffee's always nice, and reasonably priced access to a vehicle is really helpful; I'll pay $15-20 if I need one and say "thank you".
The best shop I've ever worked with: The local Lincoln-Mercury dealer. A big shop, but I usually got the same guy on writeup, who soon knew my name and remembered things about my car. He knew enough to be able to give quick, straightforward answers such as, "The brakes shouldn't be pulsating at 12,000 miles. You've got a sticky caliper, and it's a warranty issue. Leave it with us, we'll give you a loaner, and it'll be ready by 5." This after I'd paid a GM dealer for two rotor turnings at 10,000-mile intervals on a GM car, also still under warranty.
What I ultimately need from you as a mechanic is what you need from me as a physician: Respect, competence, integrity, and the knowledge we can trust each other. Give me that and you've got my business.
Best of luck--sounds to me like you're on the right track!
'97 SL500, 40th anniversary edition
'04 Olds Bravada (SWMBO's)
'06 Lexus ES330
'89 560SL (sold)
SL--Anything else is just a Mercedes.
(Kudos to whoever said it first)