As someone who frequents more than their fair share of airports, I am always unreasonably excited to find a brand I've heard of that serves something healthier than the typical fast food airport fare.
To me there's nothing better when you're just a little hungry than a smoothie, especially one I don't have to make or clean up myself. In general I find myself at Tropical Smoothie, but that's almost entirely based on proximity and not necessarily actual product preference.
I think the Jamba Juice smoothies may be the perfect consistency - they somehow found the perfect balance between a thick smoothie, where you can only finish half and juice, where you still feel hungry after drinking. They're flavorful in a way that lets you know they're fresh, but not too earthy in taste or texture.
Good beverage and average service means I'd definately return.