The U-Bahn is good but many of the lines are quite old and the connections often too sparse, specially compared to other european capitals like Paris or Madrid. There are often very close areas that take surprisingly long to travel between without a bike. I always find traveling between northern Neukölln to the middle of Friedrischain somewhat annoying unless you are very close the ring or just grab the bike and cut through Gorli. There are lots of examples like that.
Plus I find the U-Bahn rather expensive (esp. considering how little investment it seems to get) with very few buying options (only bulk-ticket is 4 rides which saves you very little) and the ticket machines seem to be broken half of the time and the ones that work are slow as hell (takes like 3 minutes to print the damn tickets).
The only plus I see (e.g. compared to Madrid) is that the stations are not very deep underground and often over the ground so it helps people that are mildly claustrophobic.
I'm coming from Boston, and wilder areas where mass transit is atrocious if available, so Berlin is amazing. My other experiences in Paris or Amsterdam are inferior to Berlin.
Plus I find the U-Bahn rather expensive (esp. considering how little investment it seems to get) with very few buying options (only bulk-ticket is 4 rides which saves you very little) and the ticket machines seem to be broken half of the time and the ones that work are slow as hell (takes like 3 minutes to print the damn tickets).
The only plus I see (e.g. compared to Madrid) is that the stations are not very deep underground and often over the ground so it helps people that are mildly claustrophobic.