Here is something I prepared earlier in the main Europe lounge thread:

https://www.flyertalk.com/forum/30449016-post749.html

I did complain by email about the delay on Fast Track security at Cologne (specifically that it was slower than main security). I got a reply back from the airport's PR people saying with refreshing candour, something like "we looked at the CCTV footage, and you are correct, Fast Track was the slowest lane. We will do something about it".

Regardless, it's not a bad airport, in my opinion, and sometimes is one of the few places in Europe where you can do a back to back with checked luggage! There again my calibration of what Hell looks like may be different to other people.