Oddball suggestion for consideration: Nebraska State Route 2 from Grand Island to Alliance. Straight through the heart of the Sand Hill Country - Willa Cather land. 100+ miles of hilly grassland. Much more interesting than the run from CO into KS.
I'm sure many folks here know about the Arkansas roads, but last year I had to drive from St. Louis to Longview Texas, and I had the opportunity to drive through Arkansas. I would have never in a million years expected it to be so beautiful. I was on the Scenic 7, but since then I've investigated Ark roads and they are quite notorious for being great riding roads. HSTA has a lot of info.
maladq, you need to ride north off 2 on any of those Sand Hill's secondary roads that run through sand hill lake country. Absolutely desolate and beautiful and no cars. Need to pee, then just stop and do it. This whole area of Nebraska is just awesome, especially if rains have greened up the Sand Hills like they have this year. Go north all the way to 275. Pick one that is pock marked with lakes. Won't regret it.
I just got back from a weekend on the Durango Loop. That was a particularly awesome ride. Especially the very technical twisty bit after Ouray. Very very awesome. Think they had to knock the smile off my face with a ballpeen hammer. Even got a by from a cop who had me dead to rights on the straight back into Durango.