I had an N900, and the keyboard was reasonably good to type on. The keys were shaped in a way that made it easy to hit only the key you wanted, without hitting adjacent keys.
I had a few slide out phones and a few BlackBerry-style phones (not BB but Nokia) and I had zero issues with either. You could type a novel on any of them.
(I’m typing this on an iPad Mini and it’s really sad how terrible the experience is compared to those tiny phones with tiny keyboards that actually worked)