For good reason too. It's not the lack of other Bitcoin affiliate networks that makes them the best. It's the dedication of the staff and the helpfulness of the affiliate community.
I've been a member for over 1 year now, but I didn't really start promoting till the beginning of this year. I can tell you from experience, The staff at RunCPA have your back. I have partnered with non-crypto related affiliate sites before and I have joined the in-house affiliate programs of more sites than I could ever remember.
To sum it up, You might come across an affiliate network that is a little larger, yes. A little better, no way.