I joined, wasn't convinced, thought I'd cancel after free trial but actually I'm coming back round to it. I'll use it as a way to screen books that otherwise I might have bought and all those .99 and 1.99s add up. So far I have made a couple of really good discoveries and bought one book to keep.
So for people wondering, give it a whirl, it is true there aren't many big publishers on board, but when you think of how many great authors were turned away several times when starting out, the same number of great writers are still out there without the support of the 'big five'. And this, for me, is a good way to go digging
Your mileage etc