I've flown CE from MAN three times in the last four months, and every time the experience has been:

• They've not bothered to open a CE/priority check-in lane until somebody complains there isn't one. After this, it's been relatively straightforward. So if there isn't one, moan.
• Issues with the number of check-in staff have been omnipresent though, again, slicing one off to do a CE queue solves that from your point of view.
• Fast-track security has been max 15 minutes, though it is always chaos the other side of the detectors. There's not enough space.
• Escape lounge in T1 is a bit dingy and windowless, but the hot food offering has always been decent and the staff are generally nice.
• Boarding is always chaos; the first time wasn't helped by the 'generic' airport staff forgetting BA use group boarding. But generally, there's often an unusual wait once you reach the gate, so don't sprint it.