I use Vortex Vipers before that i used Diamondbacks, no issues with either and both are very good for the price.
I liked my vipers however one issue that annoyed me and I ultimatley moved them along is they had extreme CA under certain lighting and angles. I recall snowy, looking towards clear sky, say at a ridgeline. Not into sun directly. I got lots of blue colors flaring.
For me, a dealbreaker. Otherwise liked them a lot.
LOTS of good suggestionsin this thread.