I just started, but the OP makes sense. I bought an ACE 250 after reading reviews by hunters. I was looking for a solid beginner unit. Went out, and quickly became a bit frustrated because the machine would beep all over.
Well, the area I am searching is VERY trashy. In fact it is so trashy that I often can't use the pinpoint function (at least that is what I HOPE is the reason). The pinpointer will squawk and yell at me for feet at a time, or will whisper at me. Basically it is useless most of the time where I am hunting. Some said I should buy a sniper coil, which MAY be in my future, but I am toughing it out.
Buy a new machine? Nope, not until I know this one THOROUGHLY! Too many people are very successful with it to be crap. Today, on my third day of hunting, I started pulling up targets almost every time I dug. I turned the sensitivity way down, and started using X sweeps and progressive sweeps to locate the target under the ground. I also stopped digging anything that had a signal that would jump all over the screen. I was rewarded with my first three coins. Nothing older than 21 years, but they are my first, and I am happy!
I will stick with my entry detector. I may buy a sniper coil for it, or a neat digging tool, but I see no need to invest in another detector (besides, my wife would KILL me!). After I have found enough to pay this one off, I MAY start saving for a more advanced detector, but only if I am SURE I have become proficient at detecting!