Ars Technica offers up a pretty decent review of the Nokia N810. They are not entirely impressed with the keyboard, calling it "mushy", but, overall, seem impressed.

The N810's built-in keyboard also falls short of my expectations. The keys are very mushy and it's easy to hit multiple keys at once by accident. I was extremely frustrated with it at first, but after a day of typing I've gotten used to it and my accuracy has improved considerably. My current verdict on the keyboard is that it could be better, but it isn't bad once you get used to it.