This is not new. Hamer came out with these in the 80's.
A parts company called Mighty Mite had one in their ads and catalog in the very late 70's/early 80's. I never saw one in person until the Hamer guitar came along sporting a triplebucker --but it wasn't until maybe ten years ago that I actually heard a guy playing a guitar featuring the 3bucker.
Guess what? it sounded pretty much like a regular old guitar...
I think the big drawback to these isn't magnetic pull--it's having to route such a giant hole in the guitar, and just try to find a replacement ring (once this batch goes out of production haha)
also, I think Nigel's octobucker is really just four humbuckers crammed together...seems like I read an article on the whole deal--the whole thing is quite silly, which seems odd coming from those guys...
edit#2: here's a link to a pic of a Mighty Mite 1978 pickup--called (get ready for the best name ever):http://www.flickr.com/photos/eric_ernest/5805772714/
gee, I wonder why Fender decided to go with 'triplebucker'