From Alabama to Colorado and back again

So we are in the middle of finalizing the planning one of the longest trips we have ever taken with the TT. We will be going from Alabama to Lake George, Co. to the Grand Canyon and back again via US40 (old route66) for a while.

We are planning on going through St Louis and picking up US 70 and heading West. Who out there has traveled on 70 towards Colorado?
How hosed up is the interstate?
Anything we need to be made aware of?
Thanks in advance