As an ATCO, I have found fam flights / jumpseating a very useful tool in appreciating different a/c performance and requirements, and also different company sop's, I never knew about E145 airframe speed limitations below FL80 or appreciated just how involved and busy the crew are during the first couple of thousand feet during the climbout. Fortunately I got to spend some time up front talking to the guys and gals.
They also gained a lot from my talking to them, about sequencing, spacing, radar separation, speed limits/restrictions.
I and all other ATCO's have been security cleared by the spooks in London, I and my colleagues wil gladly produce our airport id, ATCO licence whatever it takes.
I wasa fortunate in that I managed to get to spend time up front, my newer colleagues are doubly unlucky:
1) They can't gain this valuable experience
2) They have to listen to me drone on about the time I was on the Midland out of Leeds and we had the u/c problem etc etc etc