I have an HTC TyTN with Windows Mobile 6 and a Bluetrek G2 bluetooth headset. I am on the road for at least an hour everyday Monday to Friday, and for safety use the bluetooth haedset while driving.
I tried this hack and it works for me. However, my TyTN keeps going active while using power settings of 1 and 2. However, with a setting of 3, it stays suspended without losing connection to the headset. Perfect!
Afterward I switch off the bluetooth on the TyTN.
Also appears to lessen battery drain. Usually the battery lasts two days max, so far it's not even half drained after two full days. Definitely worth it.