Very hilly, but the course goes through various areas of Kansas City.
Train on hills.
By TG about 2013
The course is well laid out to maximize some of the most scenic parts of Kansas City; Downtown, the Plaza, Ward Parkway... In 2013 there was about a mile of the course where the street was in the midst of being repaved, and the old asphalt had been milled off, but the new hadn't been laid by race day. As a result that mile (probably between 7-8 outbound, and 20-21 inbound) wasn't very popular with the runners. There are a number of hills, though the more strenuous ones seemed to be early in the course (or maybe it was that I was just able to focus on them more early on). They had a couple bands along the route, which was great, and through some of the residential areas there were spectators with boom-boxes, and at one point even a middle-school aged kid who was playing the 'Rocky' theme on his saxophone for passing runners.
Mid- to Late-October is an unpredictable time, weather-wise, in Kansas City. The day could be 50 - 70 degrees and sunny, or 30's and rainy. 2013 had a chilly start (about 35), but after the sun rose it was a gorgeous day. Especially if you're traveling in from out of town, follow the weather forecasts closely and be prepared with a range of race-day gear.
While they provide lots of parking near the start of the race, what with the street closures, getting in can be more time consuming (especially for locals who think that 10 minutes is a 'long wait in traffic') than you might think. You may be better off parking on the street a few blocks away, and walking in.