From living in that region, I can tell you that you'll find plenty of rolling hills (which can be difficult, it can be easy to run up 1000' ascension in short order in some places), and plenty of flats, depending on where you ride and what you want to do.
If you stick to roads, you can get a good workout on some of the back-roads - they work well as many of them have been chip & sealed. Or if you deal with Knob Noster proper, there's a loop around town that's moderately traveled which will offer enough challenge for a good workout. If you're looking for trail/dirt action, there's nothing better nearby where you will be than Knob Noster State Park.
Of course, there's other good options nearby as well if you drive (or do some moderate long distance cycling - about 10 to 15 miles one way), but that can be for you to explore when the time comes.
Edit: Yes the Katy is great riding, but as they said it's mainly flat and good for day rides, touring, and strict cardio. It's a good switch-up compared to the standard MO stuff, but not too much variety in quality of ride. I recently went there (November) and posted some things in this thread: http://www.bikeforums.net/showthread...162-KATY-Trail
I took a road bike, as you will see in the pictures, so that should tell you what the Katy is about.
Last edited by Glenn1234; 01-18-10 at 03:03 PM.