I have encountered slow downs of the aircraft inbound as far east as well into Montana even a couple years back. Frequently when inbound on AA from DFW I was encountering loops last year. I do know the smaller aircraft are subject to outright cancellations as needed. What I don't understand is that I don't see full utilization of all three runways. I presume they are still too close to each other to allow true back to back throughput, but still I will sit in long takeoff lines (esp. midday) and only one runway used for takeoffs. Center is usually the one that is used ad hoc.