Go to Tiffin's!!!
I used to live in Boulder and went back to visit last week. Tiffin's was on my must-do list. They've painted it since my last visit, but it still isn't a place you go to for decor. You go there for the incredible food and service!
It's family owned and operated and those who work there are incredibly helpful. Menu items are clearly labeled vegan or vegetarian. I would estimate 30-40% of the menu is vegan, 40-50% vegetarian. The woman I spoke with said they used to be entirely veg, but economics forced them into carrying some meat to increase customer base.
They spiced the food to my liking (I love spice) and suggested items to me, as I didn't know some of the selections. The service is quick and the prices are incredibly reasonable.
I would rate this the best vegan restaurant in the Boulder/Denver area (yes, I have been to Watercourse and Leaf ... this is better)! The food is consistently amazing. The friendliness of the staff helps, as well, as they will assist you in choices and customize items. I did not see that their naan was vegetarian, not vegan and ordered it. The woman helping me asked if I was vegan, as all other items I had ordered were; when I said yes, she pointed out that naan wasn't vegan and steered me to a similar (yummy) dish that was suitable.
I also like helping out a small, family business in the increasingly chain-oriented market in the area.Pros: incredible food, wide selection of vegan options, helpful, friendly staff
Cons: decor is basic; not a date place