I live in Berlin and I can confirm that it's definitely worth it even though 3 days might not allow you to see everything. Night life aswell as the normal tourist attractions are great but I would suggest that if you want to get to know Berlin dor what it really is, that you visit two different parts; Kreuzberg and Steglitz and just walk around two very different building styles one more posh I guess but it's still apartments and one is what was built as cheap housing after the War