Fun hike! Did this one in November. Definitely worth going all the way to top! Don't skip the last little climbing stretch, you'll miss fantastic views of the foothill layers and Rocky peaks.
It has a good slow start and doesn't get steep till you get further into tree coverage.
The only negative thing about the trail is how trafficked it got closer to the top. Other than that, it's definitely worth the view!
Trail starts with hilly, open range, then passes through some nondescript forest into the more rockier, boulder areas surrounding Horsetooth Rock. The scramble to the top of the rock was fun, I highly recommend more than just looking at it! Didn't do the whole loop, saving it for another day.
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.