Hi YoungGranny,
The bike you propose looks pretty slick. I'm sure it would meet your needs just fine but it seems a little pricey. A couple of points:
1. Hydraulic Disc Brakes:
I've used both disc and rim brakes on different bikes and while I agree that disc brakes offer higher performance, if you are commuting 9 miles round trip on a relatively flat terrain, I doubt you will ever need the stopping power offered by disc brakes. If you have a situation where you are flying downhill at 45+mph in the rain and approaching a busy traffic light, then yes, you might need the performance and reliability of disc brakes.
DIY-ability:
Again with hydraulic disc brakes, you will need to bleed them on some frequency which requires some time, knowledge, and tools. Or you could let the LBS take care of it, but it will cost you ~$25 and leave you without a bike for a day or so.
The internally routed cables also look cool but they might be a pain to swap out if you ever decide to to that yourself. My bikes don't have them so I'm not speaking from experience here.
The bike below is selling for $285 shipped today on nashbar (25% off). It doesn't have as high quality of components and parts as the Trek but I'd argue it would be entirely sufficient for a 9 mile round trip commute and 30 miles worth of duathlon.
If you don't love it, you could always use it as a backup bike
Good luck with the decision!
http://www.nashbar.com/webapp/wcs/stores/servlet/Product_10053_10052_555436_-1___204734