For many years, I never quite understood the continued appeal of McDonald's. I enjoyed the occasional McRib and Shamrock Shake, but with most meals going in the $5 range, I didn't feel that McDonald's was good enough or cheap enough to warrant continued patronage. That changed a little when they revamped their Dollar Menu. With McDoubles and 4-piece McNuggets going for $1 each, it became cheap enough to say, "Sure, why not?".
The revamped dollar menu has been so successful (for corporate, although some franchisees would beg to differ) that just recently, McDonald's has cut some of their premium options from their menu, including the Angus Third Pounders, Chicken Selects, and Fruit & Walnut Salad.
My guess is that these combos are being tested in certain regions across the US, but I'd be curious if they make a big nation-wide push with this.