Logged in with my real account, I can't find, for example, "A briefer history of time" - Kindle edition, but some paperbacks are available. With the fake "american" account (and I didn't use a US proxy), I can find it (and probably can buy it).
Earlier today with the real account I could find the kindle edition but got a message "not available in your region". Now it's not there at all anymore, so I guess they are still working on things...
P.S. I wonder if Amazon is reading these forums and addapt their policies based on what they find out their customers are trying...