Qtek 9090 works with BMW Bluetooth!
Although I was somewhat skeptical before purchasing my XDA IIs (=Qtek 9090) whether it would work with the Bluetooth handsfree kit in my BMW 525d (E60) I managed to get it working! Sofar the only PDA Phone that works with BMW Bleutooth was the Treo 650.
The only difference in use with my Nokia 6310i is that the phonebook does not synchronize withthe car but that is not so bad because you can use the display of the XDA IIs to search your contacts or dial numbers. Dialing numbers through iDrive also works.
I have a Brodit 978612 holder that charges the XDA IIs and the display of the XDA IIs is easy to see. The only drawback is that you do not have an external antenna.
I did install the latest Bluetooth software (v3900) in my XDA IIs before trying it out.