The first Yongnuo product I got was a simple RF-600TX radio trigger set that I use with my Alien Bees. I've had it for over two years, used it weekly and had no problems of any kind. I can't see a need to upgrade to the big name triggers, at least for my needs.
I have two of their speedlights, the manual YN-560 and the YN-568 EX. I'm not an advanced speedlight user, so I can't comment on the fancy features, but they have been reliable in light use. My main complaint is that the instruction manual is almost useless.
I took the 588 EX along on an outdoor shoot a month ago, because I knew I'd need fill light and didn't want to carry an Alien Bee w/ stand and battery. Here's the first test shot. Do you see what's wrong? I had the swivel head tilted up one or two clicks.
When a model shoot is going really well, I like to click about every 1-2 seconds. I was hoping that with the speedlight on manual at 1/2 or 1/4 power, that it would keep up, but it didn't. I lost about one shot out of every 3 or 4 when it didn't fire. That was with alkaline batteries. I later tested with eneloops and it worked a little better.
Obviously I'm still learning about speedlights.