I tried this place when visiting Seattle recently and was grateful. Service was lightning fast, burger was simple and great, fries had skins-on and were very tasty - seemed fresh. Menu is short and sweet - just burgers, fries and shakes. If you want anything else, or really need to drive-through and not pull your butt out of your car for a sec then don't go here. Oh, and if you like ketchup on your burger you need to order that separately so don't forget!
For a quick, super cheap, tasty burger and fries - this is the place to go in Seattle. I'm from So Cal so I won't even try to compare it to In 'N Out - let's just say it's Seattle's best and call it a day, eh?