I did get mine from Buy.com, but through ebay. As far as work flow, at least for me it replaces the need to manipulate the view controls with the mouse. There are a number of ways to set it up based mostly on your preference. I haven't touched the the view keys since. There are two buttons on the device, I have one set up to goto 3D window mode and the other is set as the "reset view" command. I'm still learning the device(as well as MOI) in ortho views its very straight forward to use, panning and zooming. In the 3D view it can rotate, tilt, pan and zoom. It looks very simple
but it has a lot more functionality than is apparent. You can push or pull for straight up or down to zoom, twist the top to rotate and use it like a joystick to pan and tumble. You can also edit the axis to have them do whatever you prefer.
The device can recognize the difference between tilting forward(or any direction) and sliding forward. In other words if you were to push forward as diving an aircraft the view will pitch forward, if you keep the top flat and "slide" it forward it will pan in that direction, kind of tricky to get used to and now that I try also difficult to describe. I think the biggest thing for me as I get more familiar with it, is the ability to do multiple movements at the same time.
Yes it works flawlessly with MOI right out of the box, now if I could only model something besides cubes I'd be all set :)

The 3D Connexion site explains the axis way better than I am capable.
IMO if you can get one for $30, buy two!
I hope this was helpful

Matt