Szimpla Kert is essentially a beer garden - a very, very cool beer garden.  It is a sizable venue - a former apartment building and indoor courtyard which has been transformed into one large drinking hall.  There are different rooms with various themes and 2 floors to explore.  Furniture is more shabby than chic.  Interesting graffiti covers the walls.  Feel free to leave your mark too.  This place has so much character.  Drinks are more expensive than Budapest standards, but still okay.  Quality of those drinks is rather dubious.  The crowd is younger - 20's - early 30's.  This place is something one would expect to see in Williamsburg, Brooklyn.  The crowd is hipster-bohemian-punk rock-emo ... you get the idea.  Szimpla Kert has a great, unique spirit to it, but is still essentially somewhere, where tourists would visit, rather than those who live in Bp.  It's good for one drink on the way somewhere else, but as an established part of the tourist scene, there are many many much better 'real' options to uncover in Budapest.