BT mice are a strange subject around here, and I went through the search a while ago. I probably used 5 different models, and none of them provided the performance that I was looking for. Well, one did, the BT500, but the size of the mouse really started to bug me and I had to stop using it. (it is one of those small travel mice). Most of the issues I had with my BT mice revolved around laggy pointer performance and poor battery life, so I gave up and got a Logitech MX1000 mouse, which is great. From what I gathered, the Apple BT mouse is great, but I can't deal with the one button.
As for the BT 2.0 dongle, I have not read any reviews on how well they work with Mac's, so I can't help there. (doing a google search did provide some info about a couple of models for sell, like the one from Iogear)
Kimo