I think getitng upgraded depends on where and when you fly. Obviously, if you are flying IAH-EWR IAH-ORD, IAH-LAX, etc. on Friday/Sunday evening or Monday morning, you aren't getting UG'd unless you are a Plat. I fly ELP-IAH all the time, and choose the mainline service where possible (sometimes it's not in the evenings ELP-IAH), and I get UG'd probably 90% of the time.