This is the first I've heard of Banana Silk, so I did a search... and found this review:http://home.rochester.rr.com/bfrench/knitpics/banana/
I was thinking of trying it, but after reading that I have no idea what I would do with it.
I've used hemp in making necklaces and other sorts of things. While it's not super fun to work with after a bit of wear and tear it really softens up. Surprisingly, knitting with it never crossed my mind... but it's worth a try.