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.