I never check when I can avoid it. I travel with a "medium size" garment back and a small backpack. Virtually all of my trips require a connection at IAH, where CO typically provides a 35-55 minute connection time. If the inbound flight runs late, I typically make the connection by sprinting. I know CO has a great baggage system at IAH (I saw it at the first DO), but I need my suit later that day for a meeting and refuse to take a chance that I might make the flight and the bag might not. Just my 2 cents.