Couldn't tell you about Boston but if you ever come up to the White Mountains of NH (seems like the whole state of MA does this) for skiing, hiking whatever, you will probably go right past one of the best shops anywhere. Right on Rt 16 in Albany NH is Olson's Motoworks. Paul Olson sells very nice used bikes with a special emphasis on BMw but he works on everything. He also has a top-notch shop. I know plenty of riders who get their bikes worked on by Paul. He's very good.