I gave 'em a try when they first came out (late 80's?) and didn't see any advantage to them over standard vanes. Didn't see any DISadvantage to them though, at least none that standard vanes don't share.
I agree with Arthur. I tried them out in the early 90's. Couldn't see any real advantage to them other than they spin like crazy when you put a hard helical on them. I do believe because of their design they were a tad bit noisier than regular vanes though.
BIDELTA VANES??
