Smart Keyboard PRO. I used the trial for about a day and then paid for it. As my ancestry is Scottish, I hate to say that I paid for something when something else could have been used for free, but....
It is intuitive, but still takes a bit of getting used to. Tried Swype and (for me) the learning curve was too high.
FYI, I have a Nexus One, running stock (non-rooted) Android 2.2.1 ("Froyo")