Mill's Tavern is a great bar. There isn't any one thing I can point out about The Tavern that makes it out of the ordinary (someone help me out here). It is located near Margarita Rocks (which is a much different crowd than Tavern) next to a small courtyard where they often have bands set up during Mill Avenue events.
I never really have a bad experience at Tavern--it's kind of just one of those bars that you make a stop at when you "do Mill". Everyone who frequents Mill knows where it is, you can expect consistent service, they have a decent beer selection and pretty much everything else you need to stay afloat as a business on Mill. One thing that a thriving business on Mill needs is some type of personality. Cue Club has a personality, you better believe Robbie Fox's has a personality, every single place on the street has a personality, but I can't really pinpoint why Tavern is a thriving bar--other than the fact that you consistently have a decent to above average experience (fun-wise) and the service is great. Even their bouncers are amicable, and that is more than can be said for places like Firehouse and Chronic Tacos.
So again--someone help me out here because I don't know why I like Tavern--but I do, so that's that.