I've had a 650 for several years now and it's great. Powder drop consistency is best with the finer powders and as the granules gain in size so will the charge weight variations. I found that even with Varget I was still able to get +/=.2 gr. Maybe a lot in a small cartridge like a .223 but in a .308-30/06, not so much.
I use CFE223 for the .223 and .308 rounds I load on the 650 and have variations of .1 gr only occasionally. Keep the reservoir full, use a steady rhythm, and the ammo produced will be nice and accurate.
As for the "powder bounce-out" on the quick stop, I found that by patiently adjusting the center bolt this is minimized. Unfortunately it takes a good amount of patience as the the lock screw has to be loosened first, the center bolt adjusted for the slightest drag, then the lock screw tightened, which tightens the center bolt even more. It's a back and forth process. It pays to do this regularly anyway. Keeping the shell plate/ram head area clean pays big benefits over time. Nothing like maintenance to keep a tool in top shape.
A good source for "Improvements" to the Dillon Presses is UniqueTek.
http://www.uniquetek.com/
I especially like the tool head lock kiit which replaces the pins with screws that remove all "slop" from the tool head. Stops any "clunking" noise and if you mount a Rapid Trim, no more rattling from the motor vibration.
By all means get the primer disposal adapter. Drill a hole in the bench under the outlet, attach a hose, and run those little critters into an empty vinegar jug. No more spent primers and related crap all over the bench, floor, carpet, whatever.