Depends on where and when. On our road trip last year the Autobahn between Bremen and Köln was plain insane and probably the worst day of driving I ever had (my old car hadn't adaptive cruise control, maybe with the new one that'd be a little but better). The remainder, including the route Prague, Berlin and Hamburg, was easy going; even construction works were okay thanks to (regular) cruise control.
We did often drive on weekdays (but used public transportation in the three aforementioned cities P/B/H).
Traffic on the Autobahn follows quite extreme daily and weekly patterns. Pick the right hours and ypu can breeze through. Pick a wrong time and you'll have to contend with heavy traffic. Sometimes, the peak hours for traffic are a little bit odd. I have often seen the A81 between Ludwigsburg and Stuttgart packed on Sundays around 11pm, for example. The A8 between Stuttgart and Munich is regularly jammed on Friday afternoons.
We did often drive on weekdays (but used public transportation in the three aforementioned cities P/B/H).