"Cassette - Dura Ace 12/27"
This is the only item that I question.....Did you consider an 11/27?
"While there are a lot of Tri guys that ride Tri bikes on our group rides, I'm not sure I ready to give the TTX a run on a group ride yet."
I still don't really like to ride the P2 with a group. I'll ride it with one or two others, but usually choose the Madone for riding with others. Honestly, though I'm getting better, I do take up more road with the P2. If I draft someone on the P2, I won't ride the aerobars (and honestly I don't draft closely).
"I wish it had a fast button..."
You'll find it!
"Being retired from Biking...isn't that kinda like being retired from recess?" Stephen Colbert asked of Lance Armstrong