I've been wanting to try Motion Builder, especially since they've started their $100 free-lance offer. Despite that only being a year long licese, I think that's a great way to try out $4,000 software.
I'm glad I held off, though, because I got it for $13.50 today. The June issue of Digit Magazine from England comes with a Motion Builder disc that gives you a free year of Motion Builder with the option to permanently upgrade for $200! Cool, eh?
I bought my copy of the mag at Barnes and Noble, fortunately they carry British mags over here in the USA. To anybody else looking to try out MB, that's probably the best and cheapest way to do it.