Good info, all to be considered. I was just reading in the AFX manual that you can now edit airports 'in sim", with AFX and FSX running side by side. This is version 1.04 of AFX.
EDIT: Here's the section from the manual. Please let me know if this is different than what you're talking about.
Using AFX with Flight Simulator
Airport Facilitator X can interact with Flight Simulator in a number of ways in
order to make editing the airport easier.
Starting
It is recommended to start AFX before Flight Simulator. Both AFX and FS use
the graphics accelerator and compete for it’s resources. If you start FS before
AFX, AFX may not get enough resources from the graphics accelerator in some
cases, which may result in a very slow display or the program hanging up.
Using the FS Preview function
The FS Preview function of AFX allows you to see the airport you are editing and
all your editing actions “live” in Flight Simulator. The look in Flight Simulator will
closely resemble the view in the AFX map, but it will be projected onto the real
scenery.
To enable or disable FS Preview, use the
View|Preview in FS menu command,
or the
Preview in FS toolbar button.
After enabling FS Preview, you may want to reload the scenery in Flight
Simulator in order to get rid of taxiway signs, moving jetways and fences drawn
by Flight Simulator. AFX draws these elements itself with the FS Preview active,
and having Flight Simulator also display them may be confusing. For example,
after moving a taxiway sign, you could see it both at the old location (drawn by
FS) and at the new location (drawn by AFX).