I've got the chargemaster combo, and love it. I've only been reloading for about 6 months, so I can't say if it's going to last, but I sure do hope so. I worry about the dispense key because it's used for every load.
I load primarily 9mm, 45ACP, and 223, and find that the scale is usually very accurate. I have my setup in my garage, and with the garage door open, need to use the cover so that the wind doesn't confuse the scale. When that happens, it invariably will overcharge by quite a bit.
The scale will normally go slow when starting, speed up until it gets to about 1 grain from the load desired, then trickle until it reaches the desired load. With the wind, it seems to start slow, then go full steam until it reaches the desired load. Because the scale takes a second to register, it overcharges. As in all things reloading, you need to pay attention. You can hear the difference when this occurs and just throw the charge back in the hopper. It may be me, but I'd like for the scale to give me an audible warning when overcharged.
There may be a setting someplace, I don't know. I should have some time today to check the manual. The charge registers on the scale, and if over or under there are indicators, but no audible warning that I know about. If the cover is closed over, I never have a problem.
The other issue I find is when removing the powder charge from the scale. If the delivery tube is contacted, a few granules of powder will fall to the scale. Not even 1/10 of a grain, but annoying because the scale plate then needs to be removed to transfer the powder back to the hopper. Not a big deal, and a non-issue if you're careful when removing the powder pan. Knocking the unit will do the same thing.
I know that using the volumetric powder tools (RCBS Uniflow, Lee Perfect powder measure as examples) work quite well on the press, or stand, but being new to reloading, I'm very paranoid about overcharging the case. Using the RCBS 1500 combo, makes me a lot more confident that what I dial in, is what is in the case. Each throw is measured.
To date, I've only used 3 different powders, Power Pistol, Unique, and 4320, and haven't had a problem with dispensing any of these.
I use a turret press, and by the time I seat the bullet, and crimp using a factory crimp die, the next charge is ready for me, so there is no wait time.