As it relates to award travel, I've been playing the field for awhile. Since I'm generally flying in a premium cabin, elite status within a given alliance doesn't impact the experience. Despite that, I have yet to fly within the Skyteam (led by Delta) alliance during the last four years of heavy international travel. As of a month ago, I had less than 1,000 Delta SkyMiles in my account.
One of the challenging things about applying for loads of credit cards is that eventually you start to run out of options. Amex has a "once in a lifetime" signup bonus restriction and Chase/Citi let you receive signup bonuses every 24 months. So when there is a compelling offer that I can take advantage of, I usually do. And that is why I am going big with Delta.