David in St. Louis from St. Louis on 6/24/2009 3:40:35 PM:
Steven,
First of all, welcome to St. Louis.
To answer the second question, I would not ride a road bike on the Katy Trail, although I have heard that many people actually do it. I would say that a cyclocross is the best bike to use on a long ride (I did 61 miles on Saturday and it would have been nice), but either a mountain bike or a hybrid would be good choices (my experience is that 700X35's would work great).
I am not saying that you couldn't use a road bike, simply that I would not use my road bike, especially with 700X23's.
I moved here from the East Coast, and I love the Katy Trail. Once you have ridden it a few times, you might consider taking AmTrak from St. Louis (or Clayton, for that matter) to Hermann or Jefferson City. It's a great ride.
Good luck to you,
David