Setting this to the moisture level you want is something of a pain, especially if you want different levels in different places. I find the other one I bought, which just has a scale between very dry and very wet a lot more useful for most places. But it's strong and goes deeper, and thus more useful when i want to know what's going on around tree roots or deep in my manure pile. Buying both is useful, because I can use the cheap one with the scale to calibrate this one--after checking that the cheap one is reasonably accurate.

Bought the $100, 36" model. It was extremely poorly packaged. Looked like it had been left in the middle of the Interstate for a week. Arrived bent. Was testing soil moisture in a light shower and the next day there was a large accumulation of moisture in the meter. Took several days to dry out. Exspected a lot better quality for $100. Would not buy again.

We have 3 one cubic yard compost bins 3-4 feet deep on our farm. Bought this in 36-inch length to check moisture level at different depths.

Works good but not perfect. The calibration is a relative scale numbered from 1(dry) to 10(wet). You stick the tip in material you consider perfect in terms of moisture and then turn the screw to set the gauge to read '5'. A little touchy, if the tip hits a clump of damp dirt it will peg the meter, so you really need to do several measurements and average the results.

I'm also hesitant to leave it in the compost all them time, as there is a battery in it that might run down faster. You need to remove screws and take apart the metal housing to change the batteries.

MM17 Moisture Meter
I use this meter primarily to keep tabs on my lawn irrigation system performance. This evaluation is based on 3 weeks of use.

Durable construction:
The meter/electronics/battery box is made from 0.1" (10 gauge) thick aluminum - very substantial construction.
It has a stainless steel probe, 5/16" diameter x 17" long making it useful for lawn, plant or compost use. I expect little problem with rust or corrosion. And I don't have to bend over too far to make lawn soil readings.

Sensible design:
The meter indicator is a dial and pointer style which means it can be read in bright sunlight, unlike the digital LCD indicator types that either wash out in sunlight or cannot be read at an angle other than head-on.
The meter face is visible from above the instrument which means you don't have to lie with your face on the ground to make lawn soil readings.

Special feature:
User calibration - Ideal moisture content will vary among soil types and the kinds of plant life growing there. So no one moisture meter can tell you what is too "dry" or "wet" for your conditions. The calibration feature lets you determine what the meter should read for conditions you deem to be "good". To calibrate, I dig a test hole to the depth I want to test and see how well soil sticks to my skin. When I find a spot that looks about right, I probe close to the spot and calibrate the meter to mid scale, leaving enough dial space to indicate plus or minus deviation on future readings.

The 1 Yr warranty is better than some cheaper meters.

Negative:
Made in China. No problems yet, but, just sayin . . . things I can't see may limit durability.

From here, it is my hope that the sensitivity of the MM17 will remain consistent.

Works as well as any moisture meter and goes deeper. But the composition of soil has as much effect on it's reading as the moisture content does.
This is a property of all similar meters large and small, and it limits their utility for measuring moisture with much accuracy if you cannot standardize the composition of your soils.