I was quite fast in landscape due to the placement of everything and my ability to also rock the phone while I typed. This increased my speed dramatically.
Sadly, that is not really an option anymore as I gladly give it up for the larger real estate of the 6" models.
If I have something long to say and I'm not too concerned about accuracy, I just use text to speech.
I've tried to back this up and only found a single, questionable, data source[0] on the topic but I do attend several typing competitions and some of the young ages are phenomenal. I was beaten a few months ago by a 15 year old who was typing >220wpm+ for 5 minutes.
[0] http://drwes.blogspot.com/2011/01/results-are-in-age-vs-typi...