I'm having trouble using the Apple Migration Assistant. Has anyone had experience with this?

No, I haven't switched over myself, but I just helped my mother buy a Mac Mini. I have her old PC set up elsewhere and tried giving the migration assistant a go. It seemed to be an extremely mixed bag. It listed about 300GB of files that it found and automatically selected. It also indicated that it would bring over things like her iTunes content, web favorites, and all sorts of other user account related things.

But when I ran it, it took around three minutes. None of the music or media was transferred, and it didn't appear as though any of her documents were even transferred. What's the deal?

I did select an option at the end to "skip this user." Is that what did it? Do I really have to create an entirely new user account on the Mac in order to get this to work? Why can't they migrate into the existing account?