Multiplayer has positioning problems, sometimes even when the aircraft are standing still -- hitting PAUSE corrects these, but the moment you move the errors will creep back in. In addition, the other player(s) will often see you in a slightly different position than you see yourself (to the right of their aircraft when you're to left in your sim), or front/rear anomalies. Granted that sometimes some of this may be due to internet delays, but it's not all due to that, and it's certainly nothing to do with a server since we connect direct using IP address.
I'd like to see the tracking view restored. It worked wonderfully in FS98. In FS2002 it didn't work correctly, usually showing a fixed view from your aircraft unrelated to the player you were trying to watch. In FS2004 it has been removed completely. This is a wonderful tool for watching the other player(s) put on an airshow, for example, or for finding the other player(s) without having to either search around for a while or to use the CTRL-SHIFT-T then CTRL-SHIFT-F to get behind the other player -- which reminds me...
CTRL-SHIFT-F doesn't place you directly behind the other player -- it places you below and to the side, sometimes resulting in some weird behavior if you don't pause or slew immediately after hitting CTRL-SHIFT-F.
I'd also like to see data sent over MP for lights, doors opening, etc., just as you get for AI. even smoke on/off and contrails. Granted this would have to assume that both ends have the same effects, but you already have to have the same aircraft (or see something different -- typically what YOU are flying).
It also would be nice to see the labels for MP match those for AI, where you could ask it to see heading, etc. Sure, some of these fields are available in MP, but not all.
It would also (low priority) be nice to see the Observer mode working again.
High Priority: Do something about the conflicts between Netmeeting and FS (this may be a Netmeeting problem). In my old Win ME system, I could run FS9 and Netmeeting (NM) together, but if I changed ANY Options/Settings/Display field, I could no longer go to full screen -- I was stuck in windowed mode. On my New Win XP Pro SP2 system, the moment NM comes up the video in FS is frozen, though the remainder of the program appears to run just fine -- it appears to be some conflict within DirectX 7 stuff (yes, I have DX9.0c), but dxdiag shows a failure in DX7 stuff when both programs are running -- not otherwise.
This is high pri for me because the friend I fly with most often is still running Win98 and the game voice feature is not available to him (plus it has its own problems with relative audio levels, for example, and lacks flexibility found in NM).
I'd also like to see better control over update rate between the systems. When running broadband there's more than enough bandwidth to send data more than 4 times per second, and the parameters in the fs9.cfg file don't appear to accomplish anything in this regard (yes, we've got the same settings at both ends).
A suggestion to MS FS9 folks: Fly multiplayer over the internet (not just your LAN) connected IP to IP (not through server) and do airshows for each other, and fly in close formation, that is, similar separation to that you see in normal military formations (when in the pattern, not combat spread), though it doesn't need to be quite as close as the Thunderbirds or Blue Angels, to see the problems.
Granted there will be internet delays on occasion, but FS98 compensated for that pretty well -- all versions since have NOT.