I have been there a few times already. They have a great buffet, many choices, vegan, raw & vegetarian, including soup.
The restaurant has a modern styling and an outside terrace ( but if you want to eat outside, you have to pay 10€ more for the buffet). The staff is very friendly and helpful and so is the owner.About the food quality...everything is very fresh and tasty.The buffet includes many different salads and also a few cooked dishes, mostly with tofu, seitan or soy.And my absolute favorite...an incredible tasty awesome carob bread! It's a special recipe created by the cook and it's really to die for...:)
The dessert is not included in the buffet price, it looks very tasty, but I haven't tried it yet.
More info on there website: http://www.greenpepper.com.pt
Updated from previous review on Monday May 06, 2013
Cons: have to pay extra to sit outside