My kindle 3 (aka keyboard) works fine with my android phone's hotspot. I use it all the time. The browser is rather slow to update, so not good for browsing around, but it's good for online content high in text (eg news sites, blogs, etc), and even pretty good for forum viewing and updating (I prefer it to my phone, but not to my computer).
I haven't used any of the other Kindles, but glad to have my keyboard, good for forums, and playing text adventure games as well as reading books.