I just completed about a 200 mile stretch of Katy Trail. Spent 2 days between Boonville and Machens, MO. Conditions were excellent but for the last 14 miles east of St Charles. Heavy recent rain had me concerned but even after only 24 hours of dry weather trail conditions were excellent.
I tour on a Trek Madone road bike with skinny/100 psi 700x25 tires. Some said not do-able on Katy Trail buy I say no problem. Totally rideable even on skinny tires...and fun!. Expect a slightly slower pace though. I covered 110 miles between Jefferson City and St Charles in a day, took an additional hour, and legs were more tired than usuall.
Katy Trail is a unique and awesome riding experience. Thanks to all whom contributed to this thread..it really helped.