I live in Portland, and bikes are huge here. The most common complaint I've heard about electric bicycles is that they enable new, relatively unskilled riders to wreak havoc in heavy bike-traffic situations. This mostly involves complaints of passing too close to other riders.
This really isn't a problem with electric bicycles themselves, but with rider education.
I will also say there is definitely a sense of smugness from some riders against electric bicycles, but I'd say there are at least as many people who support the concept and want to see more people out on bikes.
Regular bikers tend to be somewhat snobby both towards other bikers, and any other types of traffic they may encounter (walkers, rollerbladers, cars etc.) So the fact that some Portlander-bikers are being annoyed isn't saying much, and I doubt there's enough of them to be a problem.
http://bikeportland.org/forum/showthread.php?t=2995
This really isn't a problem with electric bicycles themselves, but with rider education.
I will also say there is definitely a sense of smugness from some riders against electric bicycles, but I'd say there are at least as many people who support the concept and want to see more people out on bikes.