See my earlier post about UK scenery - I believe that it has been (or is in the process of being) updated for FS2002.
Concerning multiplayer flight, it is good fun. My friend and I fly this way frequently (yes we are that sad). We set up a flight in The Zone and usually limit it to 10 players or so and let everyone know which are we'll be flying in. So far, other participants have been pretty good and following real life procedures.
What is strange is that other players aircraft will lack their undercarriage (from your perspective) and if they are flying a non-standard aircraft then they'll appear as one of the standard ones often with amusing results: I flew a large jet and it appeared to others as a Cessna floating several feet above the ground when taxiing
