We've eaten at Leaf twice on different visits to Boulder. Both times we've brought groups with mixed diets (omnivore, mostly-veg, and vegan) and all were very impressed. We've sampled almost every vegan item on the menu, including appetizers, soups, and desserts, and all were imaginative, flavorful, and well presented.
Leaf is lacto-ovo but very vegan-friendly. There are enough tempting vegan-as-is items on the menu (marked as such) that we didn't feel the need to special-order veganized versions of normally lacto/ovo dishes, but it was nice to see on the menu that they are willing to do so when possible. If there were more vegan dishes, we might eat here more often.
The menu offers a sensible balance of fresh, steamed, and not-too-oily fried food, as well as one completely raw dish (the Pad Thai salad, which is super-tasty). Most of the items we tried managed to be satisfying while also being light enough that even after feasting we felt full of energy (not heavy or sleepy). The Jerk Tempeh and the starter rolls were especially tasty, and the vegan chocolate peanut butter tart is absolutely heavenly!
This is a fine dining establishment, so it isn't cheap, but considering the quality of the food and service, we felt the prices were fair and we were happy to pay them. One in our party had food allergies and our server cheerfully checked with the chef about ingredients, just to be sure.
The atmosphere is pleasant, and the location is convenient. One potential drawback for those arriving by car: finding free parking in this popular area can take time. Thankfully, the meters are priced fairly reasonably.
Updated from previous review on Sunday August 22, 2010
Cons: Not 100% vegan, Expensive (though justifiably so), Parking can be a challenge