The only thing I can add about the GT2 is that the number one concern to me is the strength and reliability of the signal...for that it gets and "A". For durability...I would give it a low "B" or high "C" rating...after all it is just a $20 radio. The GT3 uses the same receiver, so I assume it has has the same signal.
The things I did not like were, first ... the way the throttle trigger fit my finger. Not that there was anything wrong with it...it was a bit tight and just bugged me a bit. And second, I broke the antenna on the Transmitter. This was totally my fault. I can't say that the folding antenna on a high dollar Futaba or Spektrum radio would be any more reliable. Also, the wheel just seems a bit chinsy...still works though.
If you belong to a club, you may want to ask around and see if anyone has a Tactic radio from an Aquacraft Vegas that they want to part with. I am still amazed at how well these cheap radios work. New, they are more expensive than the HK radios...but the build quality is the same. The receivers have no external antenna....yet the signal strength is every bit as good as my Futaba 3PKS. I have even used this receiver in a sailboat...with the RX siting below the waterline!