I have 3 BT mice. One came with my Logitech MX 5000 Laser Desktop. This is my most comfortable and functional BT mouse. I used it with my laptop for some time, but the fact that it needs to be charged on its own charging station does not make it a portable solution. So really, it is anchored to my desktop. Beware tho, the logitech software that you have to install to use the bundled dongle is unreliable. there were a few times that the Logitech software disconnected from my peripherals, during sessions no less! Not good. I am going to replace the Logitech dongle as soon as I can.
I bought little "vanilla" Belkin BT mouse. I have a hell of a time maintaining synch with it. Battery life is also suspect.
After, having spent about $150 on the Logitech and another $50 on the Belkin, I wanted keep my BT mouse cheap. BT PC accessories aren't mature technology yet, so things can be expensive. So I looked to Ebay. I found a Dell mouse and keyboard combo for $50 new but with the USB dongle taken out of the package (I just happen to have a Dell laptop, but that is irrelevant to why I bought mouse/keyb.).
So far, I am very happy. The mouse is is small enough to be portable and the battery life seems to be good (so far). While I thought I didn't originally need the keyboard, it has proven to be a great forward thinking purchase. Now I can hook my laptop to my plasma tv and play poker on the big screen (a la Matasow) or watch videos, or whatever. Point is, I can control everything from afar, and it was a whole lot cheaper than my Logitech desktop.
This is a very similar auction, but comes with the USB dongle:
http://cgi.ebay.com/Dell-Bluetooth-Wirel...1QQcmdZViewItem