Though I do own a couple of their plugs, I'm not overly confident in NI. They have an awful track record when it comes to dropping products - almost as bad as Steinberg.
I do have their Solid Mix bundle. It works as expected, if not for the fact that they must be loaded into Guitar Rig. That being said, I can't say that they blew me away. The plug-ins merits have more to do w/ ergonomics inherent to SSL EQ's and comps than actual sound - the buss comp is pretty average, TBH.
But I don't think they're as good as the Duende stuff, McDSP's Channel G, or even Waves SSL.
And I feel the same about the rest of their plugs - none of them really wowed me. They do make great synths though.