Wow, we were on the same autobahn although I was further east... I was there three hours before you.

I found myself unable to drive after arriving in Gera, it was absolutely dangerous having the ABS kick in violently after a small tap at 10 km/h. I drove back Monday afternoon and it was much better, in a different car equipped with snow tires (Ford Fiesta, puh!).
I was only in Chemnitz and Dresden because the A9 from Nuernberg to Berlin was backed up badly and my friend in Berlin looked up the internet and advised me to take the A4 to Dresden, then A13 to Berlin. I have only been to Dresden, DDR, in 1988 but it is now very different. Berlin is the only city in Germany I am very familiar with.
Sixt has consistently gone out of their way to make me happy. I don't expect upgrades or anything, but the service is clearly superior. I am also happy with the network of Sixt car rental companies in Europe.
I only had one bad experience with Sixt in LHR about five years ago - but that was when it was new and everybody there was new. I'll be forgiving this time