Thanks for the advice.

I suspected that the $744 D fare wouldn't make it under the promotion, but I thought it was worth a shot. It still isn't clear to me how the minimum one way rule affects the promotion. I know that my direct TPA-EWR A roundtrip will qualify at $1600(800 each segment), but can't figure out if my $806 D rt TPA-AUS through IAH would qualify.
Likewise, I don't know how a multi-city trip will work out. I suppose that I will have to call CO to find out.

Still does, anybody know whether codeshares on NW count toward the promotion? Since most of the NW codeshares involve an extra leg or so, I could really rack up the segments if I had a few extra hours to spare each way.

For what it is worth, I prefer to use CO over AA. In the bad old days I preferred AA, but now I find that CO is a better experience. For one, the FC seat on the Fokker 100 that AA uses in most of the smaller markets is only about an inch wider than coach. Why would anyone want to pay for that? They also charge for liquor or sparkling water at the AC, which is tacky. Finally, connections on AA often require going through DFW, which I don't like.

As far as WN goes, I try to avoid using them because they don't have FC and their coach tickets are often only $50 or so less than CO in TX. Considering that you have to make more connections at out of the way airports(and get no miles for going out of the way), and that WN does not have assigned seating(you have to fight for your seat) and no airport clubs, WN isn't that much of a better value. The employees are enthusiastic, but that is about it.

(Of course there is something to be said for enthusiasm. Yesterday I had to fly from Islip, so I took WN. The captain walked the aisle before the flight, thanking every passenger for flying with him and giving them a handwritten letter expressing his appreciation. The passengers then gave him a round of applause, at which point many people on the flight started to cry. It was unbelievable).