I lived out there about 15 years ago, before moving to St. Paul, MN, and then Iowa to be closer to family.
Pros: About 300 days of sunshine a year, mountains nearby (which is my favorite thing to do in the universe, so it was great), lots of cool places to eat, fun stuff to do, and Coors Field is awesome.
Cons: The air quality was REALLY bad somedays - being huddled up against the mountains and having the population explode the last couple of decades and increase development has not been a necessarily good thing. I remember coming home from work on I-25 one day, and I had to turn off the air vent in my car, because I literally felt like I was breathing poisonous fumes that were burning my throat. My view of the mountains from the office was amazing in the morning, and almost non-existent in the afternoon with all the yellowish haze.
Considering all that, I would live there again in a hearbeat, I'd just live a little closer to Boulder or on the edges of town to avoid that (sometimes) bad air. Colorado is my favorite place to be in the world because of the abundance of outdoor activities that I enjoy. Good luck out there!