I am a very heavy Visa/MC credit card user. For the past 12+ years I've been Premier or better on United. Therefore, I've never had to worry about the cap on miles earning potential for credit card purchases using my United Visa. My business travel has decreased some and the places that I travel have made it necessary for me to travel mostly on Southwest (I still hate not getting a seat and no chance for an upgrade, but I've learned to appreciate the things that Southwest does well--including frequent flyer tickets that can be used on virtually any flight and a companion pass for my spouse).

Anyway, I do have a Southwest Visa. But, once you have over 100 credits in a year, you can't earn another companion pass and you have to be able to use your free tickets within 1 year. So, I'm pretty much maxed out on my Southwest Visa.

That leaves me with a need for an additional Visa/MC. I have a measly 13,000 miles on AA. I've thought about applying for the AA credit card that is free for 6 months and gives you 12,000 free miles with first purchase. That would net me enough for a free ticket. And, now that I need additional Visa/MC spending room, I've thought about just keeping the AA MC and racking up around 60,000 miles/year. (There are 6 in my family so I need to factor in the need for 6 tickets when planning frequent flyer redemption).

The other option that is almost out there is the new Mastercard Diners Club combination card. It has unlimited earning potential on many airlines and several hotel chains. But, it is $90/year and you have to pay a fee to transfer miles to airlines.

I'd appreciate any thoughts on the relative merits of the AA MC vs. the new Mastercard Diners Club card. (I already use the SPG AMEX, but I need more spending room for Visa/MC purchases). I'd also appreciate any thoughts on other alternatives that I haven't considered.

Thanks.

SDFLYER