TL;DR: Fast internet, but you need to reconnect every 30 minutes. Not many sockets, great coffee, music and atmosphere.

A charming hidden medium sized place hidden behind Kottbusser Tor. Excellent coffee, made with beans from the famous Bonanza Coffee Heroes, calm music, and fast internet provided by vodafon (needs to reconnect every thirty minutes).

There is usually at least one person with a laptop, though the number of sockets is sparse. However, after some wait, you could grab a table with a socket, and stay there for as long as you want.

Kremanski: Adalbertstraße 96, 10999 Berlin (Kottbusser Tor station).
Opening hours: Monday-Thursday: 8:30-23:00, Friday: 8:30-2:00, saturday: 12:00-2:00, Sunday, 12:00-22:00.
Size: Medium, and possible to spend many hours there.