Really useful if you're a tourist that doesn't want to appear so 'tourist-like'. Has a useful street index and map section, as well as fold-out u/s bahn network map. The little customisable tabs were a cool feature, but I didn't really use them as much- they couldve perhaps be made into a shorter section to allow for more blank pages (the reason this is 4 instead of 5 stars, really. not enough blank pages! i do have big writing, though...).
I used the blank pages for sketching and as a journal- you could also stick tickets etc in, although i found the little fold-out pocket to be more useful for that. I did not use the little rip- out 'berlin' pages at the back....nice idea, but generally a waste of paper.
It was small enough to fit in my small jacket pocket, and sturdy enough to survive a week in there! Reccomended for both first time and returing visitors to Berlin. I can't see why you would buy one if you lived there. :)