Thanks for your replies. I usually buy the cheapest tix available (kayak, etc), which sometimes takes me to Orbitz but sometimes takes me directly to airline website. Sometimes, I'm willing to pay marginally more for more miles - but rarely.

I'm looking primarily for free flights - but I'm curious what the reply would be with regard to upgrades, too. My focus is free flights.

Based in NYC, want to fly to Europe, Latin America or the Middle East; Asia wouldn't be bad, either, though!

Thanks again.