Strangely enough, my impression of today's Berlin was the opposite of Skybird's.
Regarding the former west, he's right. Lots of Turks and such.
Kotbusser Tor in Kreuzberg was the most oriental sight I've seen outside of the UK.
Wedding and Charlottenburg are not that bad, but still pretty run down.
But keep in mind the former west was a third of the city.
The former east is a rather cool place, at least when you're young.
Mitte is of course just a showchase, you can safely skip it except for museums and such.
Prenzlauer Berg and Friedrichshain are rather nice places, and actually it was really unusual for me to see so many young people and actually so many young germans on the street.
You can spent a perfect week in Berlin without going west even once.
Of course Berlin as a community is rather poor, but people there tend to be more easygoing and open minded than in Frankfurt or Hamburg or wherever.
Unusually for a capital city, rents and prices in Berlin are lower than the federal average, so that tends to attract younger people.
Depends on your age, but for younger people, I'd chose Berlin over Hamburg or Frankfurt any day.
Hamburg is just like London, only uglier: CCTV Cameras and cops everywhere and all you can do tends to be quite expensive. The city center is so clean it looks like out of a scifi movie and outer parts are pretty run down and rather muslim as well.
Hamburg has always been regarded as the most british german city and sadly this is also true for the negative. Ok, St. Pauli is cool with the Reeperbahn and Punks and the FC St. Pauli, but I wonder how long these will last.
Regarding Lübeck or Marburg or Heidelberg, I wouldn't consider those as cities. These are towns, nice towns but still towns.
I'd say Berlin is worth a travel, for younger people for the nightlife and lifestyle there, for older for the history there. Also it is by far the cheapest european capital you can get.
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