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"Very useful" would probably be an extreme stretch for this filter selection.
ND0.6: drops image exposure by 2 stops. Videographers often need NDs because they are quite limited in what shutter speeds they can use, but for general photographic use a 2-stop ND is too little to be interesting in most cases.
Grad ND: circular grad NDs, which don't let you position the ND transition anywhere but dead-center in the frame, are much less useful than a square set where you can selectively block part of the frame. The Nex-6 has pretty good dynamic range already; you'll usually be better served by learning to expose correctly and process in post.
Skin tone: unlikely that you can't also get the results you want by tweaking color in post
Low contrast: do you really want washed-out, lower-contrast, "glowy" images? You can do a lot of this in post, though a real filter can help with accurate glow portrayal around bright specular highlights --- but only helpful if you want this effect.
The CPol is the only really useful one of these that can't be reasonably well or perfectly mimicked in post processing.