My experience is pretty much like Mudmucker's. When DH and son #2 started riding in the late '90's they did get hassled/yelled at and things thrown at them. The throwers were always guys in pick ups. One time, they were having a drink and sitting on a bench in front of the west Acton Pharmacy and some guys screamed at them, calling them "fags." Huh? My son was 14 at the time and I guess those guys just couldn't take seeing a father-son bonding experience in lycra.
One time last year around this time of year, I was doing a late afternoon ride with a friend. We were riding down South Acton Road in Stow and i was pushing it, far ahead of my friend. A pick up (naturally) came very close to me (there's a wide shoulder for riding and lots of cyclists on this road) purposely, I think. I almost stopped, but just went on. When my friend caught up, she had witnessed this and got the license, so we called the police. Of course, we never heard back.
Overall, though I have had mostly words of encouragement.