Black Canyon of the Gunnison NP is worth the detour off the highway. Take the tow down the East Portal Road which is just past the entrance to the park. This road will take you down into the bottom of the canyon, a totally different perspective.
In mid summer, if you spend some time near Gunnison, take the road up past Mt. Crested Butte to the ghost town of Gothic. Some of the most amazing wildflowers anywhere in the state.
As noted, Monarch Pass is the only real pull on this route. Stop at the top and take the tram up for even better views.
Take some time to check out downtown Salida. A number of nice art shops showcasing local artists with reasonable prices. Enough great restaurants to keep you smiling for days. During the summer, they have free concerts in the park down by the river. Of course one could spend weeks exploring the upper Arkansas River Valley north of Salida. Check out St. Elmo if you like well preserved ghost towns.
The trip from Salida down to Pueblo is mostly along the river and while it has some curves, this is a scenic and easy trip out of the mountains.