Windows movie maker is started to make me throw fits. It crashes so often. I'm to the point I couldn't care less if its better than movie maker, just more stable.
WMM sucks, if only because you can't do much of anything in it. I personally don't use a free editor, but I've heard Wax is a good one and can do many effects.
I use a $50 program called MAGIX Movie Edit Pro, and I love it.
Seems like they put up the price... I was curious, so I downloaded the trial... there are virtually no improvements from version 11, and yet it's $40 more >_>
If I was going to buy anything I think I'd buy Vegas. But I don't think my computer would run it, and I'm not exactly weighed down by money right now either, so I guess WMM it is