Reagan this is my son's input at this time
 
I installed flight gear last night and gave it a whirl.

I flew their Cessna 172 (I _still_ have the feel for that), P-51, F-16,
and Bo 105 (European helo).

1.  I like the price (free)

2.  I don't like how it works with my joystick...when my joystick was
centered, the sim "saw" the stick as about 25% or so forward and 25% or
so to port.  Made everything totally out of whack.  Will see if I can
find a way to calibrate the stick

3.  Sim software is very unstable.  Got one flight out to about 10
minutes before sw crashed and took down my entire PC with it.  Had 4-5
crashes, each requiring a hard reboot of the PC.

4.  helo flight controls are, well....wierd. 
    Microsoft flightsim uses throttle as collective....throttle forward
is up-collective
        ...which feels almost natural...use "more power" for "more
vertical"
    FlightGear is backwards....more throttle = down-collective.  Counter
intuitive.
        ...doesn't feel right to "chop power" for  "more  vertical"

5.  The Bo105 model...once you figure out how to start the turbines and
lock autothrottle @ 100% and engage rotor brake....is realistic on the
ground...gradually requires more and more pedal to keep nose forward as
the rotor RPM builds.

6.  Can't really say anything else about the helo flight model due to #2
and #3....never got the feel for it due to stick calibration, and never
flew long enough to sort it out.

7.  Ignoring #2 and #3, the 172 model was pretty darn accurate.
Required just a little right pedal once the mains came up, all the way
through climb.

8.  P-51 model compared to others I've "flown" seemed horribly
nose-heavy.  That could also be #2 above. 

Summary:  Unimpressed @ this point