Good info, xlarge. Don't feel bad about giving it a try. Infomercials are designed to draw you in and make you make a purchase on the spot (free stuff when call in 30 minutes or less, etc.). They know if you decide to take a day or two to "think about it", you probably won't buy it. I would check the fine print and try to send it back. Usually the 'free' or cheap trials bill your CC for shipping at first. Then if you don't return it within like 30 days, they will add on the full price of the product. They do this so people willl think "Hey, it's only $9.95 to try it and if I don't like it, I can send it back". They know that most people, even if they are unhappy with the product, will be too lazy to get it returned within the 30 days. The company then gets the full price sale and the person is stuck with the product.
The chatter that you are getting is what you can run into with check valves. If you crank up the flow, the chatter should have gone away. You might also have below average water pressure where you live and that compounded the situation. Perhaps it is common for this thing to chatter, but most people have their meter out at the curb, so would never hear it.
Best way to cut your bill is to just cut water usage. Check toilets for leaking flappers, install low-flow shower heads, install low-flow aereators at faucets, etc. If your bill seems much higher than it should be (water usage, not price, as rates can change), there could also be a leak somewhere. In your case, probably not since it is a townhouse and the meter is inside. However, if you had a meter at the curb, you could have a leak between the meter and the house and it would be hard to know it was there (except for the higher water bill).