I've done a few, very beneficial. I'm ACS though, I think APS and TWR, especially ground movements, would benefit more. Ryanair have been offering us fam flights alot lately. Given their lack of ACARS etc, I'd be very interested to see their workload, combined with the higher workloads involved just by flying to some of their destinations; class G, non precision procedural approaches, like going back in time 40 years
