Personally, the only three programs I would consider are US, NW, and CO, in that order, all the others are too stingy with upgrade benefits (and if you fly a lot internationally, CO is too ... maybe NW too, not too familiar there, but international would bring AA back in the mix simply because all fares are upgradeable with miles then).

I'm a bit biased at this point, but you'll be doing yourself a great disservice if you don't take a long hard look at US. Tons of free upgrades, two systemwides/year, very high upgrade percentage, and tons of bonuses over the past 18 months. They have pretty decent service out of MIA/FLL/PBI, though it has been cut back a bit, but tons of 757's/A321's, which are the best planes for upgrades anyway, and pretty decent service out to SEA from the hubs, mostly on Airbus aircraft, which are very comfortable.