You are free to choose

It depends on what you are interested in. Cryptography, Computer Vision as well as Virtual Reality and Machine Learning / Webinformation Systems has really competent teachers. When I was there, also Mobile Systems and Usability Engineering / Cognitive Systems was really interesting and well taught. In general, professors are good to reach and interested in helping their students. If you are good and motivated enough you can publish scientific papers (depends on your skillls).
Class rooms are small and the computer pool really crowded and noisy (especially at thebeginning of each semester, thanks to the freshmen).