I just received my A&D scale and you really can't compare it against the GemPro.
I used the GemPro 250 for about two years and it wasn't bad. It was accurate, drifted occasionally and pretty reliable. It had to be on 24-7 to get consistency out of it. During a loading session, 50 rounds...drift was experienced 2-3 times. Hit the tare button and back to normal. In all honesty, I don't think hitting a tare button constutes a bad scale. In the A&D manual, it specifically says to hit "re-zero" key before each weighing to eliminate possible errors.
The main reason for going to the FX-120i is speed. The GemPro would take 3-5 seconds to register anything dropped into the pan. So when getting close to charge weight...it was a constant cycle of drop 1-2 kernels, wait, drop 1-2 more, wait, repeat and hope its not over. The FX is insant and consistent when weight is removed and set back on.
With the GemPro...it took usually 2 kernels of R15 to move .02, maybe three depending on size of a kernel. Certainly would not register 1 kernel of R15.
All in all, the gempro will get you by...as long as its a good one, lol. I've read guys getting turds and sent them back for a replacement. One nice thing is, CS is great on them and will replace the scale if you encounter any trouble. The manual sucks though...there is a good YouTube video on scale calibration...find it and follow it.