I wonder if there is any difference in the BT hardware or drivers on the i9100 and the ATT i777 version??
Im running the latest nightly of CM9 for the i777 and I get the PIN Code entry as well over here.
I just tried following the instructions here for manually entering the MAC address in Wiimote Controller, but when I put the Wiimote in discovery mode and tell Wiimote Controller to connect, it sees the Wiimote but in the Notification Bar at the top I now get a notification that I have a BT pairing request.
If I click on the notification, it still brings up that same PIN Code screen so it definitely doesn't work on CM9 with the stock kernel here.
I may just give in and try the latest ATT ICS leak for the i777. My Android native games are ok using the touchscreen but man playing NES and SNES rome on here sucks with the on screen controls hehehe.