Not read this whole thread but I'd like to chime in...

Best: Omnisphere, Stylus, Trillian.  Just amazing for the value.  I'm shocked these are as cheap as they are for as much as they do, constantly hitting us with free updates, they work flawlessly, never crash.  I can't imagine anything that's close to these or that I find more useful.  Melodyne gets honorable mention.

Worst: I buy most every sample library I can, I think I have at least 500+ libraries.  There are a ton of duds in there.  Maybe 25% of them I've found to be completely useless for one reason or another.... either bad production, useless timings, completely disorganized messes, etc.  I figure the duds are just part of finding the good ones.  Anyway I don't have time to make a complete list but I always welcome messages asking about a specific library, I'd be happy to give anyone my personal feedback about a library before they buy something.  You could send me a PM.