The first batch of N800's have a known problem where after a few weeks of use, the right side of the device (left side if you're looking at it) stops responding to touch or can't be calibrated accurately. Since there is no way other than the touchscreen to access many of the device's functions, you then have to send it in for repairs.

Nokia will not reimburse you for the shipping cost, and has a very broken tracking mechanism. As several users at the Internet Table Talk forum have documented, this means that your $400 device goes back to Nokia, and you don't know when/if you'll get it back.