I do have a regulator on my setup, What I found off ebay, I believe, is a regulator for paintball. I am no paintball expert but I believe they use them to maintain constant pressure when firing?
Anyways, they have ones with fixed pressure (which are usually in the 100's of PSI, but after looking hard enough I was able to find one with a low working pressure, that was also adjustable. I keep the working pressure @~50psi
Here are some images of an extra setup not in use, the setup I am currently running has a better (swagelok) needle valve.
Working pressure gauge on regulator:
On/off on top of paintball regulator:
I try to keep the working pressure to about as low as it will go.
Also note that the gauges both read the same pressure, so it wont tell you when you're running low (but when your bubbles stop or your working pressure drops its time to swap tanks).
That being sad it's a lot better than just the on/off valve, and was only about 30 dollars for the regulator so I did the upgrade because I already had the system. However, if I had to do it over again I probably would not go the paintball route and do a 5lb and cga-320 regulator.