I'm also using the Delta Plat AMEX till I hit the 25K spend, then will be whatever card I need to hit a spend bonus on. The MQM's are what drive the spend there. Secondary right now are USAir Premier World MC and Priority Club Visa for when AMEX is not accepted. Was also mostly a debit card user till last year when I convinced the other half how many great places we could go with the signup bonuses alone! Also got her to go on her first MR with me in late 2010 (the DEQM out of Nashville). She still thinks I'm a slight bit insane, but loves the perks!