eww, Xah Lee has a nice introduction to using EWW. There's not much to know, really, but Lee has a short FAQ on how to do some of the things that aren't obvious if you hate to RTFM.
I've kicked the tires of EWW but haven't used it extensively. Some knowledgeable folks, such as Nic Ferrier, think it needs more work but it's still loads better than what we had before. It's hard to see how Emacs can ever have a good embedded browser until someone embeds WebKit, or something like it, in Emacs core. There's been some discussion about that but I'd guess it's still pretty far off.
In the mean time, EWW is good enough and will probably be an excellent solution for looking up documentation on the Web. I've got a lot of that bookmarked in my browser but I can easily see adding a bit of Elisp to bring it up in Emacs instead of having to switch over to the browser.