I've been using my PS3 and a Keysonic wireless keyboard for TV browsing for a couple of years now. Most of the navigation is done with the dualshock, with the keyboard used only for text entry. Once you get used to the dualshock controls, it's very easy to navigate around pages and quickly zoom in and out to make text readable. Flash video works pretty well, and a big plus is that (as far as I know) there aren't any PS3 viruses, trojans or botnets to worry about.
I bought my parents an Asus eee Box to do the same thing, and that works really well too.