I have the D-Link BT USB adapter that I bought for my old 17inch Widescreen iMac (Luxo-type). I am now using it on a 1.25 G4 eMac. Panther makes it easy to set up. If you haven't ordered yet, I'd vote for internal, too.
Going "over the top" with OTA, Netflix, Drobo FS and Apple TV!