Things do not work well in general. DB is internationally infamous for its garbage service because everyone who has ever taken DB has a horror story. I lived in Germany some years ago and not once did I manage to catch a train that was on time for both arrival and departure. And this doesn't even touch on the topic of being stranded in the middle of nowhere as a regular occurrence.

Depending on what regions/lines you are exposed to one can definitely land on different sides of "it works well in general" vs. "it doesn't work well in general".

Of course if you cite a Sprinter line like Nuremberg <-> Berlin, which has the newest tracks and newest trains, you will have a far better experience than on lines that have the worst maintained tracks and trains. Sadly, the badly maintained ones seem to make up the majority of the DB network.