There's been a smattering of information post the latest fw upgrade, so I thought maybe we could re-post experiences with various headsets with the newest upgrade. For my contribution:

1)GSM (Cingular) 1.17/1.51 and Treo Wireless Headset. Honestly, I haven't noticed a lot of difference except that the range appears to be somewhat (not greatly) better. The volume and connection speed has always been good and they haven't changed.