As per title, just updated my A320 with the A330 firmware and it works perfectly (not sure if it makes any difference but I have the ILI9331 LCD driver on my A320). Had to set it to English (same deal: push all the way to the end, hit down 5 times) and that was it. Everything functions the same and the menu layout is identical, about screen reports model A330 version 1.2 firmware lol.
Not sure there's much point aside from the new look but hey, now I have an A330 minus the controller for free!
Update: Christ, everything is identical to A320 firmware aside from the main icons and the background picture. There's nothing new going on here aside from minor cosmetic changes.
The other difference I forgot to mention is the start-up screen. It's an animation of an iguana (I think) and it's not that great IMO. A little bit crude, it's just a GIF file.