I live just around the corner of Weser Vegetan and go there quite often (as many people who live in the are). The food is the best of this category (vegetarian turkish food) in Berlin in my opinion.
The "Wunschteller" which means you can combine 6 different Antipasti and hot dishes like hallumi or sigara börek is incredible. The place is run my a family and they are so helpful and kind.
The atmosphere...well it's nor a proper restauant of course, otherwise it would be more expensive. The place is clean and you can see they made an effort with the decoration, unfortunately might not match the taste of most people who go there (ikea pictures on the wall, light chains...), but with some little changes they could actually make it nice. Anyway, not really important...and outside it's really nice in summer!