I've done the TAT (Tenn. to Moab) twice on bikes. Have yet to do the far western section.
The section in the Ozarks of Arkansas is great but then Oklahoma gets a bit long, flat, and boring to be honest. Then the very short New Mexico section is awesome, followed by Colorado which is as you would expect, fantastic.
This September I did the "Heart of the West" on my KTM 640 Enduro with my friend on his XR600. It's a loop of nearly 3,000 miles through parts of 6 states, CO, WY, MT, ID, UT, NV:
My ride report is here :
A few pics from my HoW ride:
This would be AWESOME in my truck, albeit much more expensive. (my bike gets 55-60 mpg). There is great camping along the way.
It doesn't have the technical passes like the TAT but makes up for it with the epic views, expanses, and the historical aspect of the Oregon Trail, Pony Express, Trans-Continental Railroad, etc.