We have one at the medical fitness facility where I work. In general I like it. Because it's free for us to use I have done a few tests over the years that would probably cost me a ton to do if I didn't have access to it.
It is fairly solid if you follow the rules correctly -don't eat or drink before, remove heavy clothing & metals, etc. I've done test-retest fasted vs 30 mins after eating a few times, and the numbers can be wildly different, as much as 3.5% body fat 'change' so take that advice carefully.
Under similar conditions, my numbers have been fairly steady. I've never focused on hypertrophy, fat loss, etc. in my life, and my numbers consistently hovered between 1-2 total lbs, skeletal muscle ~1-2lbs and body fat ~1%. This is over a period of over 5 years. As my training was mostly strength/velocity geared, these results match my expectations given volume, training emphasis etc.
I recommend repeating the same conditions on retest to get best value (same time, same fasted time before, etc.). Personally I find a coffee in the morning doesn't affect the score, assuming I use the restroom prior (otherwise water numbers can be thrown off. Another important point to follow regarding following instructions).
I actually just did a test-retest after 8 weeks of taking creatine, and am up 3 lbs, 1 of which is water, 1 muscle and 1 fat. This was accompanied by 1x a week heavy strength training, and ~2x week of more medball/jump circuits focusing on high velocity.