N9 keyboard has also been thanked a lot on the reviews. Nokia has probably created the best tactile feedback for the keyboard there is on N9. iPhone and N9 keyboards are different, but i would rank them about the same.
iPhones advantage over N9 could be that it knows to throw special characters on the main keyboard when you need them (example when typing email address there's @, typing domain name, you got .com), not needing to go in to miscellaneous characters

Though Lumia 800 might indeed just have the best keyboard of any TS phone i have tried. Coming from a guy who have owned, or owns GS, Iphone 4, N9 and Lumia 800.
It got amazing way to register just the right buttons even when typing quite carelessly.