I just got my Firefly remote working with Boxee thanks to EventGhost which is truly excellent software. A plus is that EventGhost takes the place of the bloatware that comes with the Firefly remote (BeyondMedia, etc).
Step 1. Hook up your SnapStream Firefly remote and install the drivers (but not the beyondmedia, etc).
Step 2. Install EventGhost (www.eventghost.org)
Step 3. Download the attached xml file and open it with EventGhost
And it should just work. It is quite nice to have use of all of the control buttons instead of just up, down, left, right and select.