There are several threads by Fusion owners, but I'll give you my bottom line: I've had my suit for a little over a year. I have about 200 dives on it, in salt water and in caves, including some bottom crawling in Florida and some exits on my knees in Mexico. I absolutely love the suit, to the point where my backup suit is my HUSBAND's Fusion, and I never wear either of my other two drysuits any more. I have had no leak problems at all (except things I've done to the suit, like replacing the neck seal and putting in a p-valve). The exterior Lycra skin shows almost no wear at all -- a little pilling on the legs from crawling on limestone, is all.
The flexibility of the suit is unparalleled. It's extremely easy to dive. One does have to clean the inside of the suit and lubricate it with a dry lube to keep the lovely, slippery easy of entry, but since the suit is trivial to turn inside out, that's no big deal. It rolls up and packs beautifully and weighs almost nothing.
This is one cool suit.
