I don't own any Vortex scopes, but I have played with a few of them now in a variety of light conditions, and have a good idea of how they perform. I would place them in the intermediate category so far as quality goes, which is not meant to damn them with faint praise. This is a pretty broad category in which a LOT of manufacturers fall. Definitely better than BSA, Simmons, Bushnell, and similar lines. I don't think they are as bright under low light as standard Burris or entry level Leupolds, but otherwise the quality seems along the same lines. The Burris Extreme Tactical line is really more in the upper levels of quality and is comparable to the high-end Leupold scopes, so I do need to differentiate on that aspect. The Vortex does seem to hold a zero well, have fairly precise movement when adjusted, and is able to hold up to some rough handling, so those are all very important pluses. A few people I know have these mounted on AR platform rifles in calibers from 5.56, to .308, to .458 SOCOM, and no problems with any that I know of, and I know of one mounted on a H&R Handy Rifle in 45/70 where the owner is using pretty hot loads and it hasn't come apart, so they don't seem to be sensitive to recoil. From this, I would say that they seem to be a pretty solid performer, especially for the price point.
To the comments that they are comparable to Nightforce, Zeiss, high-end Leupold, and similar...not even close!! If you want to really see the difference in how your optics perform. go out in the woods on a moonlit night and see how far into the shadows you can penetrate. Stay in your blind until full dark and see how many extra shooting minutes you can get from the higher quality glass. See how absolutely precise and repeatable your adjustments can be with the higher quality scope. I've done numerous side by side comparisons of this sort, and there IS a difference between premium scopes and intermediate scopes. Is it worth paying 2x-3x as much? That's your call. I hunt pigs at night a lot and have other uses where low-light performance is critical, so for me the answer is "yes". I also have personally experienced that sinking feeling when, as you sit in your perfectly placed blind in that dark hollow where even at full noon you are in the shadows, when that monster buck walks out just as legal shooting time is ticking away, and you can't see your crosshairs well enough to justify a shot. That particular deer still haunts me, and that was the moment when I made the decision to invest only in quality glass from then on. With Zeiss, Nightforce, high-end Burris, Nikon or Leupold scopes, this is not a problem. I guess it just depends on what you expect from your scope. If you plan to shoot only in decent light, then Vortex and similar value-priced scopes are definitely an option. If you want to extend your shooting time to include those critical 5-10 minutes in the early morning or late evening, or in low-light conditions when you may not want to use a light, you may want to spring for a bit more scope.