In November we found out that Assist in our '04 X5 wasn't working. I was told that I would have to go to the dealer. I retrofitted the '05 Assist/Bluetooth combo TCU in the X almost a year ago and figured I was screwed since I replaced the OEM TCU with the '05. After talking to the service manager , things looked favorable, the TCU I put in was still under warranty (and the X5 is too) . The part number they showed to replace the unit I installed was on "national backorder" and the only way to get a new one is to open a PUMA case with BMW tech. We got the car in, PUMA case opened and part ordered. Had a few problems when the part did come in (bluetooth wasn't working) but they quickly determine the tech put the wrong TCU in the car (they had two an OEM one and the one from the PUMA).

On to the results....
sound quality seems to be a little bit better, but my wife can't tell a difference.
The major thing I noticed is the interaction with the phone. We have two SE 610 phones and prior to this, the initial directory upload too a long time (over one hour), this time it took about 10-15 minutes. Also, the phone (handset) was basically unusable when paired with the car, you couldn't navigate through the menus, make calls, etc. This isn't an issue anymore, it is very responsive.

I don't have the P/N in front of me, but it appears they have made an improvement on the part.

-Jeff