I used a Stimpson for a long time at my last job. Opened my own shop now and it wasn't in the budget yet, so I picked up one of the signworld machines. So far, I'm please with it. I've used over 1000 grommets with no issues. I added a plywood base and mounted a caddy to it for grommets (found the caddy at Wally World in the shower section).
It's not as 'polished' and it's slightly more difficult to use, but for $69, it's WAY better than using a hammer....