And for an admitted clyde (or anyone, really) what difference is a few pounds? What magically changes at the 20# mark?

Anyways, service at Performance varies a lot depending on location, as there is variance between other non-chain bike shops. A lot has to do with the quality of the manager and staff at the location. But either way it sounds like you're interested in learning to do most stuff on your own down the line, so having the best ever mechanics at the shop you buy from probably isn't a huge deal.