We used Meinfern bus a couple of weeks ago from Dresden to Berlin. The bus was scheduled to leave at 6pm but didn't arrive until 9.10pm. When it arrived, the destination changed from Berlin Alexanderplatz to Berlin Zob. So, we had to take the Ubahn to our hotel instead of walking like we'd planned. We arrived at the hotel past 1 am instead of the scheduled 10pm. It wasn't a big deal for us cause we had no luggage, we were determined to experience bus travel in Germany and we're not bothered by such chaos. And, it gave us a chance to moan with locals. However, it might be quite annoying if you have time and/or other constraints.
Pluses: the fare was 6 euro per person from Dresden to Berlin, much cheaper than the 29 euros supersaver fare we paid to get to Dresden. The bus was comfortable, had a clean toilet and free wifi. They sent us a text at 6.45pm to let us know that the bus was delayed however they didn't know when it would arrive. They sent us a 6 euro voucher for future travel as compensation for the inconvenience.
We would definitely use them again but just want to let people know about our experience.