In my experience it's different not better. Bacon is the prime example; a good butcher's bacon will dry a bit leathery; thick with a smokey flavour and runs that's chewy or crispy depending on how you cook it. Supermarket bacon is thin and pumped full of water but it's greasier so more satisfying fried and the dripping can be used separately; you just don't get that at the butcher's.
Besides that who knows. It's going to depend on the butcher, when you go there and how much the butcher likes you.

>how much better is the produce in the farm veg boxes poshos get?
Not really the same thing but I know for certain that my local grocer(')s stocks produce of huge quility over supermarkets. Absolutely massive potatoes, onions, capsicums, etc. I havn't been in there for the past few years so I'm not sure how the weather has effected their business.