I have the keyboard 3G version, too. The web browser is very basic and buggy, but it works for simple sites, such as gmail (if you load the lite version). It seems to lock up a lot, especially on sites with Java. Obviously it doesn't do flash or anything requiring a decent frame rate.
What I do find very useful (and very niche) is that our public transit is all tracked online via GPS on simple web pages. Since I don't have a smart phone, I can check arrival times for when I'm out using the Kindle 3D.