I, too, can confirm that they have not 100% fixed this issue with 6.1. There is a minor improvement for me, but I still must "remind" my phone that the BT device I am switching to is Handsfree. I use my BT car system (Infiniti G35) and a PLT510.

The minor improvement I found is with the car. I used to have to make a call each and every time I got into the car, even if I hadn't use the PLT510 between. For some reason, my car BT system would not fully connect with the phone...it showed on the car's BT screen and all, but when a call came in, the car wouldn't recognize it and I'd have to answer on the phone. So to make the connection each time, I got in the habit of calling VM each time I started the car...and I'd have to select "Answer" on the car even though I had made the call directly from the phone...after that quick VM call, incoming calls would come through to the car just as they should.

Now, when I make that initial VM call, I don't have to select Answer on the car -- which tells me that the car and phone have already fully connected, so that's an improvement with WM6.1 (albeit slight). I have yet to run a controlled test and receive a call in the car without having first made my VM outbound call...I am hopeful that it'll work fine now.

Interestingly, my PLT 510 has no problems switching between what it is paired to. I have it paired both with my i760 as well as a base unit on my office phone. I can shift between them and the headset connects seamlessly to either. Sad that the i760 itself is less capable than the headset for this function (I say "function", not "feature").

BTW -- IMO, there are other improvements with 6.1 that make me, so far, overall glad to have upgraded. Still diagnosing some other problems, but the "goods" at the moment outweigh the "bads", at least for me.