I 2nd the vote for the RIM 655. It is not perfect but is better than all the others I have sued and I have used near 10 different ones. Not a big fan of BT headets, but there are times in the field that I got to have both hand free and the 655 does better that any I have seen.
I could only ask that they make the buttons on it less hard to push. I think that the pressure required to push the main button is a little excessive.