Why 5 stars? Because this is the best coffee you'll ever find at an airport.
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Of every airport I've ever been to, I've never found a coffee spot as awesome as this. You really don't feel like you're inside an airport while you're waiting on your beverage of choice. I think it might be an optical illusion, and not actually inside the walls of Sky Harbor.
Not only are the drinks delicious, but the trendy decor is as hip as it gets. And while service can vary hour by hour, the barista who happened to help me was incredibly friendly.
There aren't a ton of details one can procure from a four minute experience, but Cartel was as good as it gets across the board: taste, service, and ambiance = 3 thumbs up!