I've not yet had opportunity to put it to actual use in a real project yet, but I picked up an inexpensive EBay model.
I have been able to verify that it works, but as far as I can tell, it doesn't seem to have a "re-zero" feature, like the alternate low-price model options posted above may have. (It does have a "compare" feature which basically accomplishes the same thing, but it needs to be manually activated to re-zero after powering up each time. It's not off from zero a big amount, a small fraction of an inch of water. It's just sort of a minor annoyance that it doesn't read exactly "0.00".
)
I will say I very much like the compact size, but perhaps they are all similarly sized. (For reference, its smaller than my Fluke digital multimeter.) I believe it will work great for doing basic diagnostic work. First project I'll probably use it on it is tankless water heater supply gas pressure diagnostics.
But I can already tell it's much more compact, convenient, so much more precise, (and hopefully more accurate) than my home-made "water U-tube" manometer, which I made years ago and got some good use out of on a home-made airflow tester, which I used very effectively for custom racing intake manifold development.