I've used some cheap glass by NcStar, Leepers, Simmons, UTG, etc. and have had ok results. But I've also used Bushnell and have a nice vintage B&L on my Marlin 336 (Father in law's old rifle).
The cheaper Chinese stuff (my Bushnell is Chinese, but doesn't have the same problems as the cheaper ones) don't hold up to recoil. Even the simple red dots will wander, sometimes after only a few shots. My AR pistol is light recoiling, and sports an NcStar 30mm RDS, until I can replace it with something better. Most of the other cheap chinese optics are in a box and haven't been mounted to anything in quite some time.
They do work, and I've found some are much better than others. I tend to use them on lighter recoiling rifles like .22 and 5.56. I had one on an SKS for awhile, too, but it wasn't really tight and spot on. But then, I wasn't trying for cloverleaves at distance. A low mag optic at 100 yards or under for "combat accuracy" was my intended purpose, and for the most part, they were able to maintain that.
But I found quality irons to be more accurate and much more reliable in the long run.