I'm pretty nonplussed by them, but one thing that annoys me is when they use the road rather than dedicated cycle paths. Theres a long, straight-ish road near me thats a 40mph limit, and has a dedicated path set away from the road for cyclists. Not only is it there for the safety of the riders (i know i've never done under 45mph on that road, its too long and straight) but also when they're riding at less than 20mph, you have to slow down and try and wait for a break in the oncoming cars to pass them. This pisses me off. They seem arrogant.