We just did this road a couple weeks ago. Much improved over 2003. There are some occasional washboard spots in Wyoming and Nebraska. However, unlike 2003 when more than 50% of it was washboard and heavy construction areas, now there are much fewer construction areas and most of the washboards have been eliminated.
If you like stopping at Wal-Marts, be sure to catch the one in Laramie. Most lovely sunsets and sunrises there and a nice store to boot.
Chicago is a mess to get through so we bypassed it using Route 30. Saved some tolls also, as I80 becomes a tool road all the way to Ohio.