I've been cycling the Sammamish/Burke-Gilman trails (mostly Sammamish) for 20 years and have seen just about everything. If I had to choose, I'd pick the agressive riders over the casual riders and pedestrians. I'm not letting them off the hook for their "I'm coming through so get out of the way" attitude, but at least they are competent cyclists and have some idea of the rules of the road. Really the only time they bother me is when they pass me while I'm overtaking or passing someone else, especially when there is a cyclist or pedestrian coming the other way. I have had far more close calls with casual cyclists/walkers/roller bladers/kids than I have ever had with agressive cyclists.