I have a viper hslr 6-24x50 and like it. Tracks good, glass is decent for the price. Only complaint is the redical is pretty fine. Hard to see sometimes in low light especially in the timber.
I own a few 6-24x50 pst gen 1. They all seem to track very well and the glass seems good for the price point. The main issue I have been having is the reticule on one of my rifles likes to break free and rotate in the scope. It is currently on the way back to vortex for warranty work after only 40 some shots from the last time I had to send it in.
I've got the 4-16x44 Viper, I like it a lot. It's sitting on a .300 wsm and I haven't had any issues wiht it. Pretty good glass for the price. I've got the HST version, exposed turrets for easy adjustments and the reticle is hashmarked with moa and the bottom post is hasmarked further than the rest to allow for longer shots. Like a couple guys said, the reticle is thin. It's definitely designed, at least it seems that way, for long distance shooting rather than hunting, judging from the thickness of the reticle. But that said, still a really good scope.