I originally purchased THIS DIFFERENT KEYBOARD Ultra thin Slim Bluetooth 2.0 Wireless Keyboard Keypad for iPad 16GB 32GB WiFi, iPhone 4 4G 3G 3Gs Sony PS3 Smart Phones PC & Mac Laptop Desktop Netbook HTC Nokia Sony Ericsson Motorola Samsung LG Blackberry Mobile Phones
from Amazon, however found it to be unacceptable for the PS3 even though it was advertised as being compatible.
Anyway, I decided that an official product was the way to go and I do not regret this at all. The keyboard feels VERY sturdy and is deceptively weighty which inspires confidence in the build quality. It takes 2 AA batteries (I bought rechargable Duracell batteries from Amazon).
Pairing with the PS3 was almost instant (2-3 seconds) while the keyboard in the link above took over a minute to be discovered by the PS3 and had to be paired every time it disconnected (i.e. you had to press the PS button, go to settings>accessories>manage blutooth accessories>pair device!!). This keyboard will disconnect (go to sleep) after a certain time when not being used, but you just press the PS button on the keyboard to wake it up and you are connected again!! This leads onto my next point. Two big positves about this keyboard is that there is a PS button (like the one on the controllers) and there are the square, circle, triangle and X keys on the keyboard. The square, triangle etc buttons are on the 'F' keys so you just need to press FN + F2 (F2 relates to square on the keypad for example) or whatever button you need.
It doesn't show on the picture very well but there are left and right mouse click buttons on the bottom of the keyboard as well so would extend its value further than the PS alone..
All in all, an excellent, solid keyboard that works flawlessly with the PS3. Buy it.