I bought one for $2.49.
The Triple Cheeseburger tastes both meatier and heartier than a McDouble or Double Cheeseburger. On this occasion, the beef patties were actually juicy (I'm guessing they were fresh from the grill), but someone must have gone a little crazy with the salt and pepper while cooking them because there was a sharp salty bite throughout (it's a shame given the rare juiciness).
Unfortunately, the onions, ketchup, and mustard get lost in the shuffle with the enhanced meat and cheese proportions. I missed them for the most part, especially the onions, which are fairly light to begin with.
Nutritional Info - McDonald's Triple Cheeseburger - 6.8 ounces (192g)
Calories - 510 (from Fat - 240)
Fat - 27g (Saturated Fat - 13g)
Sodium - 1150mg
Carbs - 36g (Sugar - 7g)
Protein - 31g