You mention the complexity of the ASP.NET membership system. I've always found it to be quite straightforward (unless you write your own providers I guess). Where are the pain points for you?
It was quite difficult for me when I first tried to pick up ASP.net. In retrospect, I don't think the problem is how difficult ASP.net provider system is, but the absence of assertiveness in the voice in tutorials. They tend to say, you an do it this using Forms Authentication, or Windows or Passport. Which is all true, but presents too many options to someone trying to find their way around a new system.