In an IC(E), I can open my 13" Laptop and work fine, even if the person in front of me lowers their seat. On the particular bus I was riding, the table was just too small. Plus, the bus has much more unexpected movements than a train, I couldn't even look on a tablet screen for too long without feeling some travel-sickness. It was a very long, very boring ride.
The WiFi, btw, was a joke on the autobahn. It was working a bit in the cities...
Also, the trip took more than an hour longer than was planned, and the traffic on the autobahn was absolutely fine (I did the same trip with a car a couple of times). Driving into the cities took lots of time, but again the traffic probably would have looked the same any other average day.
It definitely is cheaper though...