I disagree. Berlins transport system is nice, but it is far from perfect. Ever have been there in the winter, or try to get on a bus when you are the only one waiting on a bus station? Berlin is famous for having many problems with their transportation system, some result form bad planning and technical and financial debt, some are cultural (people are unfriendly).

The metro in Paris is way nicer to use - more reliable, cheaper, drives very often and has a far reach. Same goes for Vienna and Hamburg.

I even prefer smaller middle sized cities systems, in France and Germany, at least on the day when they are working - and if they are not completely stupid, like causing themselves to be always late by letting the bus driver control the bus ticket. But I disliked Berlin in general.