I know a gyro on the ailerons will correct the tendency many soaring planes have of trying to roll out of a banking slow turn. I don't know what else a gyro could be used for on a sail plane. I use a rudder gyro on all of my warbirds. Makes takeoff and landing easier.
inputing some rudder (going into turn, for instance) over-rides the gyro, so I don't really have to fight the gyro for control.
Be careful how many servos you hook up to a gyro, they WILL drain your rx battery faster. Since they are more or less always making small corrections. One on a rudder OR one on airlerons won't drain it too fast, but four servos hooked up to a gyro may be a major drain.
In my experience, the cheapest rate gyros work fine in airplanes....heli's need expensive (heading hold) gyros I hear. I bought all my gyros (I now have acquired about nine of them) on e-bay. I know all the horror stories about e-bay, but I haven't ever had a bad transaction. I bought one Helimax gyro for $9.00
My last purchase on e-bay was a Saito 100 (new) for $124.00, which included $6.00 shipping.
Are you sure you saw a newsgroup thread about the gyro? Some time back I read an in-depth article on some guys soaring web page about the use of gyros in soaring planes, but I didn't bookmark it....sorry
opinions will vary, JK