I have a few of them in small foamies - EDF, 3D, and one Warbird. They work well. For example in my 63" F-7F Tigercat (Flightline Foamie) I have the airplane a little aft CG for my tastes without the gyro on. For flying with or without the gyro, I have programmed the usual mixes to make it fly like a pattern plane (rudder to aileron and rudder elevator mix) so it will hold true knife edge and slow rolls can be done accurately in spite of a powerful rudder to roll coupling tendency of the airframe. While I've set up the plane to fly true aerobatics without the gyro, such as described, I love what the little gyro brings to the consistency of the tracking and behavior in calm and in windy conditions (it's a light weight model afterall). It just "flies bigger". It flies well without the gyro and does not need the gyro for typical warbird flying but as a "pattern warbird" platform it is as responsive as it needs to be and yet as stable as it should be to fly accurately. I also have a small 52" long Mig-21 foamie that I love and it does not need a gyro. I flew several months without one, but when I fly it really, really slow and nose high... the wings rock quite a bit. Yes I know Deltas do that... but real Mig-21's don't rock back and forth at 120 Hz in slow flight and it makes the model look, well, like a model... So I put the gyro in to make the little -21 fly like a larger plane at high alpha and in higher winds. I've yet to be discouraged from flying this model in wind. The wing rock is gone with the gyro and she flies "bigger" but just the same, still - it's still a Mig-21, if you know what I mean. On 3D what I like is they give you confidence to get more aggressive and fly lower while pulling off the boilerplat maneuvers you'd normally only dare one mistake high. I've learned in 1 season what might have taken 2 or more.

I am not sure of their reliability over time... My experience is my experience but in terms of statistics, probably an invalid sample size! But for what they are, and the fact that you can get them for $20, and the fact that on my specific applications they have worked really well - I can not complain in the least in the applications I've chosen them for.