Hi All, I had been experiencing the same issues as discussed - new iphone 4s would not pair via bluetooth with car stereo, macbookpro, ipad2, all that I had previously paired with the iphone 3gs that the new phone replaced.
I thought ' perhaps it's an issue with the fact that all items had been paired with 'my' iphone previously', so tried deleting the previous 3gs pairing on the MBP and then was able to successfully pair the 4s with my MBP.
Excited, I went to the car and removed all past pairings with the car stereo (very scientifically, by disconnecting the battery; I need bluetooth before preset radio stations!) and straight away the pairing worked - no endless swirling of the 'searching for devices' on the 4s, instead the device (car stereo) appeared straight away and paired immediately.
I haven't tried the ipad yet, but anyway...
Maybe it's just something that worked for me, but hopefully this may help others recover from that 'oh man what have I done' 4s upgrade feeling. 🙂