I don't know much about the 150, because I just bought the 250 after reading all of the positives from people here at TNet. I've had it about a week and my coin count is going steadily up, rather quickly actually. Here a few things I've noticed that will make your life easier and get you going faster. This is all stuff I read here on TNet. If you're not a charter member, become one if you can. The search option is great. I searched for ACE250 and read everything I could to get the helpful hints.
The detector sounds when the outside edge of the coil passes the object, not the center. This is the most important thing on the ACE250 I read here. This makes it very easy to do the initial pinpoint. Then use the pinpoint feature by holding in the pinpoint button. You'll find your objects much faster doing it this way. In just the last two nights I've started finding, digging, and recovering sooo much faster. This is important if you only have an hour or so to MD at a time.
The other thing is to really get to know the signals. In just the last week that I've had the detector, I've been able to really learn what the signals are going to identify.
And the last thing I'll say is that it might be easier starting out to use the coin mode and then discriminate the nickel signal. I seem to get a lot of junk with the nickel icon undiscriminated.
These are just the things that are working for me. The most important thing is probably just to spend as much time swinging and recovering. This is the best way to learn this detector I think.
Good Luck!