Have you given Swype or Shapewriter a try? Rather than hitting each letter, you slide from letter to letter and it predicts the word that you want. I use Swype as I found it to be more accurate, but both apps use the same idea, and I find it to be much quicker than the standard typing method. I am not great with links, but just search for "Swype" and you will find plenty of information. Also, it is not in the market, but you will find a link in one of the threads you find.
My last suggestion is to give whatever app you choose a few days. I did not like Swype the first day and uninstalled, but decided to give it another try and it is definitely the way to go.
i think you should still try the physical keyboard as well. my hands are large as well and the first couple of days using the keyboard i had a hard time as well. but now here i am a month later and i always use the physical keyboard and i txt as fast and as accurate on it as if it was the htc pro 2 keyboard (best keyboard if you havent seen it.)
Thanks for all the feedback. Oddly enough, I've been having more success with the touchscreen keyboard vs the physical keyboard so far. Maybe I will get used to it, maybe look in to Swype. I think these units are built for munchkin hands.
There are a few keyboard replacements in the market (better keyboard, smart keyboard) that have gotten some good reviews on here. I am currently using sype as others have mentioned.