I've jumped on the F4:AF bandwagon recently.
Now, I've never had to read a 700 page instruction manual for a video game before.. but it was actually worth it overall. If you're new to the game, don't bother with any simplified settings. They'll just confuse you later on when stepping up the realism.
A couple things...
When the original F4 programming team was let go, a few weeks later the source code hit the net. This is where all the mods came from (FreeFalcon is good, but I'm more of a BMS/SuperPak fan). A few years later Lead Pursuit started working on F4: Allied Force with Atari as the publish
Atari are nutjobs. They require a written release and approval for any mods put out for the game (or else they sue you).
F4:AF has vastly improved multiplayer stability over the original F4.
The graphics are not improved. This sucks since F4 had outdated graphics when it was originally released in 98.
The campaign system is the best of any game I've seen. Ever.
I haven't had a single crash to desktop since the last patch, and the new features are great. I've already setup the shared memory data server and F4:AF Glass panels. It's nice to have a laptop screen full of gauges seperate from the PC I'm playing the game on... It helped me stop trying to do split-s merges against cons on the deck and pancaking myself. If you have a second PC or multi-monitor setup, this stuff is incredibly useful.
Lastly, I'm buidling a 5 day long (real time!) Tactical Engagement with 800 aircraft, 200 helos, dozens of divisions, 24/7 AWACS & tankers on station, and a mean air defense system for North Korea 2010. Going to host it on my dedicated server (w/ TS!). If anybody is interested in playing (bring a squadron!) drop me an email for more details!