The idea of the Egg White Delight is pretty simple: Take the standard bearer Egg McMuffin, replace the fried egg with egg whites, and the American cheese with (pasteurized processed) white cheddar cheese. It's such a simple idea, I'm almost amazed they hadn't thought of it sooner.
After suffering through numerous dry, rubbery, flavorless egg white omelets at restaurants everywhere, the Egg White Delight* is the first egg-white-based breakfast I've had that's actually worth eating. It's missing the richness of the yolk, but it's otherwise indistinguishable from the standard Egg McMuffin to the point I'd be hard pressed to tell the difference if I ate them blindfolded.
The Egg McMuffin was already a reasonably good breakfast choice at only 300 calories. The Egg White Delight knocks off 50; at 250 calories each, you can have two of them and it's still an almost virtuous breakfast option. Or, you can substitute egg whites on any other breakfast sandwich. Considering the weird spongy texture of the square egg that comes on the biscuits and McGriddles, the substitution is a no-brainer.
And now, on to little ol' Carl's Jr.