I find it pretty straight forward and easy to use. If you're looking into getting into digital comics, I would certainly recommend it.
EDIT: I forgot to tell you that if you want to use the reader you need to click on the Comixology logo on the home page. I don't think any of the buttons on top take you to it. I've decided to read Fables first arc instead of Superman Secret origins as my next read after BY1. Just out of curiosity, I see it's for is for Mature Readers, how much adult content is there in the series? I read the first issue and there was a fairly tame sex scene, is that the worst of it and it's spinoffs or does it get more explicit? It's not going to keep me from reading it or anything (True Blood is one of my favorite shows, and I watch alot of foreign and indie movies, so I'm not exactly easily offended), I just like to know what I'm getting myself into beforehand. Same question for Y: The Last Man, DMC and Witchblade and it's spinoffs.
I was never a regular Fables reader, but it's less bad than Hellblazer, I think? Btw, don't read any "100 greatest comics villains" lists till you read the book, because they'll spoil it.
I can't really speak for Y: The Last Man, either, but it has some nasty parts I think, violence-wise.
It's Vertigo stuff. So probably about half as bloody as your average Green Lantern book, but there might be some nipples or penises on occasion.
Witchblade, I've always assumed is the most deeply unpleasant kind of comics sexploitation--that is, not even honest enough to call itself porn, and not drawn by either Kevin Maguire or an Italian. People might tell me I'm wrong, but it's right there! On the covers!