We didn't do the loop, but just did the Horsetooth Rock trail out and back. This was gorgeous even in November, it was really nice to hike through some pines and get views in multiple directions at higher elevation. A fairly busy trail on a Sunday morning but it didn't detract from our enjoyment of the hike. The elevation gain is pretty steady throughout but going back down sure was nice! Horsetooth Rock itself is slightly intimidating to climb up on if you aren't fond of heights or drop offs, it isn't technical but is very exposed if you truly want to get to the top. Even without climbing up, there are spectacular views at the top - seeing the snow topped mountains in the distance was beautiful.
Hiked the Horsetooth Rock trail. Relatively easy trail. Saw families, dogs, etc. the last portion of the trail up to the peak of the rock did involve some steeper climbing up rocky faces. Lots of options to extend or shorten the hike along the way.
I hiked this trail several years ago in summer and enjoyed the dry heat of Colorado opposed to the humidity in New England. The hike offered lovely views, a manageable terrain and a cool waterfall. We were with friends and young kids so this is a definitely a family-friendly trek.