i'm a merchant mariner and wear this on deck aboard a sea going tug/barge unit where we've encountered some heavy weather in the past. I was always concerned about accidental inflation with ordinary automatics, because when its worn, its because I had to go out on deck in some nasty stuff, usually in the pouring rain and the seas whipping up over the deck edge. The hydrostatic inflator solves that concern however, to make sure it inflates when i actually fall over the side, not when I'm drenched from head to toe from the weather. Its a similar mechanism to those found securing the life rafts to the deck and made by the same company, so one can reasonably trust it, but when in doubt, theres always the pull cord, thats why its there.
I found this vest to be well fitting and of good quality construction, it should hold up well to the abuse. it wraps around your neck and shoulders comfortably and is flexible to wear when working that you forget its there sometimes. This compared to lesser models by other manufactures that feel like the vest is hanging on your neck and is rigid against your body at every move. The SOLAS tape on the inflation bag, whistle, and strobe attachment are nice touches as well. I plan to add some solas tape to the outside (mustang does make another model with that on it from the factory, but for more $$), but other than that small personal deficiency, its a great product.