OK. I definitely won't be buying miles, as it wouldn't be worth it for me, but I might take flights on other *A carriers. I haven't considered Air Canada because I don't see any need to travel to Canada, unless it would just be miles with them and I fly with a different carrier. Btw, I like the idea of US Air DM and going on different flights, but would I be paying US's mileage fee or the chosen carrier?

Thanks for all of the help.