Well... I wasn't going to get all into it, but since you brought it up... The reason I bought it in the first place WAS because it didn't cost $300. I have a whole thread about it - but short form:
Ever since I had the regulator, it would always take 2-3 weeks of tinkering with the settings to get the flow to be consistent after replacing the tank. I would get the bubble rate set at a good pace, and I would come back an hour later to find that all of the pressure had gone and I would have to adjust all the knobs to get the flow going again.
After almost a year the solenoid went bad and would never kick on. I called Milwaukee (who I will say were EXTREMELY helpful on the phone) and they instructed me on how to purchase a new solenoid and get the regulator working again. I did this, and it worked again for a few months - but the same as above.
Then a about 2 months ago I came home to find all of my fish at the top of the tank floating vertically, gasping for air, and the tank had so many bubbles it looked like 7up. All of my cories were huddled together in one corner dying together, rolled on their backs, gasping. This happened twice that week. And to a lesser extent a third time.
So I will say that is probably a dramatic example, and not really very common. But I also definitely say that I am a firm believer in you get what you pay for and peace of mind is something that I'm willing to pay for. I travel quite often on the weekends so, to know that I have a quality regulator that isn't going to have a flare up like this is priceless.
I suppose I should edit my response. I love the MA957, but I also use a pH controller so that things like over-gassing never happen.
I can buy a pH controller and MA957 (brand new) for less than the cost of a nice/fancy two-stage regulartor.