If you've been to any of the Northstars in Columbus, Green Dog will be very familiar to you. It's an almost identical concept - line up at the counter to order, food is brought out to you, minimalist design, and an emphasis on locally-sourced ingredients with a lot of vegetarian friendly dishes. They even have magazines for you to read. (I believe the similarities to Northstar are not a rip-off: I recall reading when GD first opened that they'd consulted with the NS owners. So it's more of an homage).
I've been here a number of times for all three meals, and liked my food every time. This may be heresy for my fellow Columbusites, but I like GD's veggie burger better than the vaunted NS one.
Yes, if you see the counter ordering and thus expect a price point that is like Chipotle or Panera, Green Dog will seem expensive. But I feel the prices are
reasonable for the quality and quantity of food you get.
It's a little off the beaten-path for most tourists, in a newly-developed strip mall in Columbia-Tusculum. But well worth a visit if you're on the east side of town.