At the top navigation bar, I'd have a Products tab and a Services tab. That would let you see what was offered regardless of device (important because sometimes new devices are compatible with old ones or because some people have more than one device). I'd also consider adding a Reviews tab up there instead of having Reviews buried on the bottom right of the page.
In the Your Device section on the right, I'd have drop-down lists to choose the device instead of the "Change your unit" (which sounds dirty
) link. (There's also the red bar at the top showing the device and having a change link, which seems redundant.)
Finally, I'd suggest stepping into Web 2.0 and adding a blog. They could have tips and tricks to keep your device working well, sales notices, stories about odd PDA accidents, etc.
Steve