Out in the open (that is, outside of the municipalities), open carry is generally no problem. There's nobody out there that cares or notices.
Now, within a town or city, it varies. The problem in Kansas is the lack of preemption - you're pretty much covered if you have a CCW permit, but lacking it could be rough. I'd personally speak with any police departments or sheriff offices in the county/city you're going to open carry in beforehand to know what kind of response you might get to open carry. Manhattan unfortunately is a college town and there are many idiots around who see a gun in a holster as a nuclear warhead waiting to go off. As usual, caution must be excersized.