It's Bluetooth (like the headsets and controllers) so it doesn't need any dongles. It comes a with a USB cable so you can pair it easily (you just USB to PS3 once and it is paired) and you use this to charge teh built in rechargeable battery as well. It auto turns off or standby's so the battery lasts a very long time imo.
I have one, and think it is worth it, if you use the keyboard a lot, you will use this a lot. Take a bit of getting used to where the extra symbols and stuff are, but you can type fast once you learn.
rp2000