The browser has been enabled in the UK for several months now.
http://kindleworld.blogspot.com/2010...r-expands.html
The usage is free; the bandwidth fees are usually for moving personal content of bringing ebooks from non-amazon stores. Yes, you can buy DRM-free books from non-Amazon sources. Plus, of course, you can side-load via USB.
You may also want to look at Calibre's Web server and book emailing features; they make accessing your own ebook collection via the browser easy.