I live in Grand Island, Ne and have pulled my 5th wheel both directions on I-80. By washboards, are you actually referring to the expansion joints in the concrete? If so, they are there and will always be there. I dont find them too terrible but I may be used to them. I dont remember ever coming across actual washboards. I have found that the inside lane is a tad smoother for some reason but you still have the clickity clack of the expansion joints. Hwy 30 is a nice drive but I actually prefer the interstate when pulling my camper.
Safe travels...
Jon