I actually have the above linked Sony Bluetooth Wireless Transmitter for iPod, unopened and still in a box. I accidentally ended up with two of them, woops. I have used one of the extensively, prior to the 3.0 upgrade, and here are my thoughts:
1) If you are not moving the iPod around while using it, the signal is solid and clear. I used it in the lab all the time, and it was great with my headphones because I could just place my iPhone in the middle of the lab and walk 30 feet in any direction without loosing any noticeable audio fidelity. The iPhone is paired with a Motorola S9-HD headset.
2) For some reason, the second I put the iPhone/BT combo in my pocket and tried to listen to it, it blew hard. I have heard this does no happen to other people though.
PM if you have any questions about the unopened one in my possession, may be able to help you out.
