I used to live in Arlington (just north of Cambridge), and I would ride everyday down Mass Ave into Boston. I've never really had a problem with it, and I find Cambridge to be a fine place to ride a bicycle. Yeah, the bike lane kinda hugs the door zone at times, but that's why you stay out of the bike lane in those places.

One of my lasting impressions of that commute was the difference in road quality between Boston and Cambridge. I always found the roads Cambridge to be relatively smooth and easy to ride on (for the most part), but literally as soon as you cross the bridge into Boston, the pavement's a disaster. Mass Ave in Boston is an absolute wreck.

One of my all time favorite stretches of road to ride on is Mass Ave going through Harvard Square heading south. you have to swing around to Mt. Auburn St. for a bit before you get back on Mass Ave, and there's this banked hard left turn that's tons of fun to take at high speed. Wheeeee!