I know this is no help in your situation, but in my own personal experience, CO is not that great on upgrades.

In 1996, when I was flying CO out of Houston, I in a span of 6 months, I managed an upgrade exactly twice. And this was in the period where Delta Platinum Medallions got upgrades on all fares (including L fares) at the time of booking.

Again, this is just one person's experience, but I just question the value of CO's elite level programs. I really think you could do better in another airle's FF program.

Just to clarify...CO's program is a really good one in most aspects, but I (personally) have really bad luck in upgrades.

And, BTW, you better not hope you ever get a celebrity (like Barbare Busch) on your CO flight. They will delay the plane, let unqualified Secret Service people act as gate agents (with attendant lack of customer service!), and then lie to you about the cause of the delay.

In any case, why not look elsewhere..and the best of luck whatever!

-Harry