Hey dex, I am a big fan of this scale (VIC 123). Mine works pretty well: it reads a class 5 mg weight at .021, .022 or .023 and my Mettler H10 reads it at .0226.
On page 13 of the directions are a list of parameter settings, I chose to use 1.1.4 and 1.3.3, leaving the rest factory (1.1.4 resets the environmental sensitivity of the scale and 1.3.3 resets the decimal place sensitivity).
With these settings in place, the scale takes about 5-6 seconds to settle into a reading, but I'm sure you can spare the time. Also, warm up the scale ( for at least 5 minutes) prior to use by turning it on, leaving it on and maybe putting a small amount of weight on it and doing a quick calibration (you can calibrate at 100g, 50g and 20g; if you have a good 20g weight that may be the best choice since you're weighing in the mg ranges. If not, the 100g supplied weight works fine). If you do not let the scale warm up properly it will not return to zero with any regularity, and will further throw off your reading.
Also, I've tried using extension cords with other items plugged in (phone and Mettler H10) and the scale went sort of haywire, giving very erratic readings- meaning: plug this scale into the wall, do not use power strips or outlet three ways, plug the scale directly into the wall outlet.
If you have any other problems after adjusting the settings on pg13 of the manual, and allowing warm up and making sure that you have proper voltage, please PM me and I'll see if I can help. As I said, mine reads almost spot on with a scale that reads 0.1mg. If I can help i'd be happy to.
There are better scales out there, but they start new at near $1000. This scale is worth $250 IMO.