Windows Movie Maker is my love/hate affliction. It seems everyone has had some problem with it crashing, being slow, not rendering properly, etc. I also hated how I had to convert my clips. Now that I'm using Ubuntu, I miss Movie Maker, because it has an interface like no other, I guess. It was easy to use and easy to manipulate to get pretty good movies, and in conjunction with Wax 2.o pretty cool effects.
Now there was on other thing I meant to say and I now I can't think of it. :/
Oh yeah, WMM limits your outputs! You have no choice to keep the exported movie the same quality as the raw files. The newer WLMM is a bit better but abandons some of the more useful features and the timeline bar...so it's a tossup.
Right now I'm using Openshot because Kdenlive bugs out on me every time I try and use it.