Rula Bula is among my favorite bars in town, and is easily my favorite place on Mill. They have a great atmosphere with awesome live music, and while it can get crowded on busy nights, it's never so packed that you can't move around. The patio is great year-round (they have heaters for when it gets "cold"), and they have a full bar inside and out. The inside is gorgeous and feels classy without being pretentious.
As far as prices go, they're not the cheapest, but it's reasonable. The best part is they have a great whisky/whiskey selection - amongst the best in Tempe (if not the best)!
I can't recommend Rula enough!