i'm using it. it works generally well. the music selections are so-so, but you can upload your own if you want.
it's sometimes pretty slow to load, but not terrible.
the fact that clients can add comments is very cool. unfortunately, i get a lot of clients who email me right after they try to submit and say "hey, i had some technical errors with that site...did you get the comments?" i always have, but it's frustrating that my clients (most of them) seem to get errors when they submit. (but I've been too swamped to follow up.)
also, i asked a while back for a 'confirmation' message when the client submits comments or approves the book, and it hasn't been added. i've had one client accidentally approve.
soo...it's a great idea and a good start to a product, and certainly worth the cost, but i think they need to be working on the development a bit more.

(otherwise someone with a comparable less buggy product is going to come along and i'll switch without hesitation.)