I25 from Sante Fe to Pueblo CO is one of my favorite stretches of Interstate highway. Lightly traveled between those two towns (as there's not a lot of truck traffic) and beautiful scenery. Gets very busy around Albuquerque, Colorado Springs and Denver though.
There's a mountain pass (Raton Pass) between Raton NM and Trinidad CO but it's nothing too bad. There's an RV park right at the top of the pass with great views. They have a restaurant too, but last time I was through there the restaurant was closed.
2004 National Dolphin LX 6320, W-22, 8.1, Allison 1000, Front/rear Trac Bars, Hellwig Rear Anti-sway Bar, Sumo Springs, Roadmaster Reflex Steering Stabilizer, 2005 PT Cruiser Toad