Just to open up the topic again, I use the Think Outside Stowaway keyboard; admittedly I don't use it extensively, but I'm on the same batteries as when I bought it in December last year (I don't remove the batteries when I'm not using it, so the battery life is pretty impressive). It also switches off automatically when you close it.
It has a spring loaded cradle (that can be removed if you wish); the PPC is not secured in the cradle, so it's possible to knock it over, but to be honest I don't use the cradle - I just lay the PPC down flat (less chance of claiming on my insurance that way!

)
The keyboard is seamless, and it's impossible to see any join when it's open.
The down side is that the top row of the keyboard is used for the QWERTY line of keys, the number keys (using the blue Fn key) & the special characters such as !@# (using the green Fn key). It doesn't bother me, but apparently some other users aren't happy with it.