Used it... loved it!

At my previous employer we trialled 360 degree feedback for the senior management team first, and then extended it down to line managers (of which I was one). It was certainly an eye-opener for a lot of the staff, me included, about how your contribution to the team is valued, and how your skillset appears to others.

I'd definitely recommend it, if only for the "wow, do I really come across as an ass" factor which sometimes surfaces unexpectedly ;-) We found it was great to really improve a team though - team meeting after all feedbacks had been discussed individually with manager/staff member, and everyone presented one element they wanted to improve on.