a while back there was a guy trying to sell one on g.b.'s forums. i think he wanted 9 bills for it. i tell you, i sure was thinking on it. the only thing that stopped me was i already had a f.a. in 44 mag.
the only downside to the 50ae that i can think of is brass availiblity. bullets might pose a problem depending on where you live. and the brass is going to cost more than a standard calibers. having said that, i have no other experience with the 50ae. never shot one, never have had a discussion with anyone who has smote and animal with one, either. i woud imaging it would work very nicely.
i think it would be a fun gun, definately unique. also, i never heard anyone say "damn, i wish i never would have gotten this f.a." everyone i have talked with loves theirs, no matter the chambering.