I've got one and have been using it for just under a year now. It's good to do the ocasional checks. I still use my beam scale to check it with when I am setting up a reloading session. I'll use it to weigh every few rounds after and they are always pretty close to accurate. I've never been off more than .2gr +/- when loading. I keep my loads pretty much in the middle of the road load wise so the .2gr isn't going to under or overpower me at all. If you're a max loader, I wouldn't use this scale for anything serious.
As for the automatic shutoff, when I'm reloading, I get into a pattern where after so many rounds, I hit the power button and when it sets up, I drop the test load on it to wiegh and keep going. it shuts itself off and I hit the button again a few charges more.