I've just begun implementing some web services with WCF and so I'm in the midst of learning the ins and outs of the API. First off, it's phenominal as I'm sure you've heard if you already know if you've read about it before. What you might not know, if you haven't played around with it yourself, is that the documentation is still pretty shoddy at this point. It definitely seemed to make some progress in the June CTP, but it still seems that if you want to do anything past the basics you really need to dig around and figure it out for yourself. What's funny/frustrating is that a lot of the documentation outline is done, so you'll see that there's a topic available to answer your questions, but then you click on it and you see a page filled with "Insert content here". For example: Sending Faults.. :\ Luckily there's a lot of people out there writing articles, blogging and of course there's always the MSDN forum for WCF too.
Maybe I'm just spoiled by the plethora of WPF documentation that is available. Gotta give that team some serious kudos because they've consistently delivered some of the most up to date and complete documentation I've ever seen for a pre-release product.