The M Gates area is very dull. Don't plan on making any bargains here or get any great food (gates here mostly used by budget carriers ie easyJet and Norwegian).
Flying BA from gate 26. Security before entry into area no liquids/ pastes. Don't cross the line until you need to. they can't guarantee places to charge up you phone like on the KLM areas
Don't waste your free WIFI time. It's limited to one hour (2 x 30). Also, if you're looking for a jack to charge your computer/phone/etc, look for the wooden tables which have black electric jacks.
Fairly awful centralized passport control on connecting flights. They should have many smaller control points like CDG and other civilized airports. Prepare for a 30 minute wait.
If you are a business class traveller avoid KLM like the plague. Fill all seats in European flights so no extra space. On Intercontinental flights their business class seats are from the dark ages.
My second time at this airport flying back to EU from US. I went through Orwell-like security check, worse than the US one! They want to go even through your wallet! Don't let them. This is insane.
They “renewed” the security check before you go to the gates, but i can tell you with one word it’s shit! Everyhting takes to long and you don’t even have a business or fast track entry. Really bad!