Almost a year--and no issues! Wow...China's got it all figured out now, baby. lol
Pixmedic is not the responder who I was expecting....but do note: he has ample flash experience AND has FOUR individual Yongy's. For the person who wants one, single speedlight, and is going to count on it working with Nikon commanded CLS triggering, and who wants FULL power, not "a stop less" and not "one and one-half stop less power" than a Nikon SB 800, then buying the prior-generation's top-level, professional-grade flash at a used retail price is a smart move.
The people that have one,two,three, four units have ample backup flash units, and usually a lot of flash experience, and are willing to trade reliability and 100 percent compatibility for low price and disposability. I get that, and I respect that. But for the person who is "getting into" flash, and who wants to buy once, buy right, I say go OEM flash. The added full stop of flash power is something the secondary-level units,even OEM flashes, LACK, and which can never be recovered. If a person owns just ONE, single flash unit, something like a Nikon SB 800 or SB 910, or a Canon 580 EX-II, is a very valuable piece of equipment that can be depended upon. The 100 percent compatibility issue....for example, WayneF mentioned that a Neewer 750 flash unit did not work properly with the now-ancient Nikon SC-17 cords he's kind of fond of, but he was willing to live with that as a "tradeoff"....consider the price of an SC-17 cord used, $10-$15, versus the $69 to $89 new-model SC-28 or SC-29 cords Nikon makes...
I have a 30+ year old SC-17 cord that works impeccably..and I have three, 1980's-made Nikon flashes that still fire. Yongy has not even been around as long as a bottle of bourbon I bought last month.
With a used Nikon flash, the old,outdated cords made in the eighties still works...but NOT with a new MIC knockoff flash...
I totally get the idea and allure of having low-cost flashes that work,mostly, but not 100 percent with the cameras some people own...but my advice skews a different way for people with limited gear and minimal kits they want to maintain/supply with spares/support with redundant backups/throw away when busted.
I don't recommend cheap knock-off gear to beginners, or to people who own one,single speedlight, and want to actually count on it 100 percent, for years. I feel that beginners and intermediates get the most "boost" from the high-level gear; experts can finagle and DIY and troubleshoot any old gear...I don't like retreaded tires or discount coffee or refurbished mattresses...but all are great deals, or so I hear from folks who buy those kinda things...