I figure it depends on what your buying it for and just how high (or low) you set your standards. If it's for a play gun never to be used outside of plinking or range time, you don't care if you have to fire off extra ammo because the sights drifted and what not, sure go ahead. It's your money and if you want to buy several to replace broken ones, more power to ya.
If it's on something a bit more serious like a match gun, might work for you but make sure you can take loosing a match if the accuracy isn't up to snuff or it just plan quits working. If your ego is easily bruised, then you might want to get a better sight that will hold its zero and hold up to abuse.
Finally, if you're buying one of these things to put on a firearm that will have a chance of seeing duty in a self defense scenario, I'd run the other way from one of these things. Maybe your life and the life of your family is held to pretty cheap standards but me and mine isn't. When it comes to anything I plan to use to defend the lives of me and my loved ones, I spare no expense to ensure that my gear is good to go from a trusted reputable source. If this is your plan, you may want to reevaluate your priorities, think things over, then avoid the cheap Chinese junk and get the good stuff.