The Aquatek, Milwaukee, and Azoo, and their clones, will all be functional. But they're single stage, and low quality, and are far more likely to bust than any of the used industrial regulators many of us use and repurpose for our needs. In addition, there will be an increase working pressure as the cylinder nears the end of its fill, potentially causing problems unless you keep a careful eye on the pressure.
Furthermore, the needle valves on those units are identical, and extremely imprecise. They're functional, but barely so.
As for the solenoids, I've read little to suggest they're any more likely to fail than many of the other solenoids we've tried over the years (reasonably likely), but mine did, in any case (I had a 3M, nearly identical to a Milwaukee).
Generally, responses will vary from "love it" to "will never entertain the possibility of using one again in this lifetime", with nothing in the middle. Basically, you get what you pay for. In this case, the all-in-one rigs are cheaply purchased because they're cheaply manufactured.