i hope 4.2 addresses the BT issue.. i think its a little better than 4.1 but still other people on the line say i sound "mechanical" when i go more than 5 feet away from my iphone 4.. i am using a 975 too.
I've quite enjoyed the ability to dial facetime email addresses from the iphone and also I've gotten accustomed to gamecenter and think its a nice addition.
It was worth to me, but people who don't use these two features may disagree.