I've just been fiddling with my sat-nav after using it extensively on my recent trip through Austria, Italy, Switzerland and Germany.
I noticed that it has recorded a maximum speed for the trip of 129mph, which I reached (legally and safely) in a brief burst on a completely clear stretch of the A5 between Basel and Frankfurt. The Alfa 159 (2.2 litre four cylinder petrol version) I was driving at the time felt like it had more to give, but I would have required a much longer piece of empty road to max it safely.
But don't go thinking that the Autobahns are a high-speed paradise. Long stretches of the A5 have a 120 km/h limit, have only two lanes in each direction, or are clogged with traffic - that means average journey times probably aren't much better than they would be in the UK.