And don't forget, the N800 has an fm radio, the 810 doesn't. You will probably buy a gps unit for the N800, and you can move it around for best reception. With the N810, you have to put the gps wherever the N810 is, since it is part of it.

So when you're cruising on the Queen Mary 2, you put the gps unit against the window and lie in bed holding your N800, checking your position and speed. With the 810, you probably have to get out of bed.