I have 2 Incipio cases for my GNex and I highly recommend them both. For those looking for moderate protection, the NGP is a polymer case that protects the entire phone (except screen). It is grippy, light weight and has generous "bump outs" for the volume and on/off switches that allow perfect access without false activation. Given the material it is composed of, it is a bit thinner than the typical silicone case and therefore adds a little less bulk to the phone. It cost around $16 from Amazon. Mine is black which goes well with the phone. It is well made, comfortable in the hand and has no visible or tactile mold line. I have an Amzer silicone case and would guess that the Incipio NGP provides the same level of protection as that case or any other silicone case like the Ditztronic case.
Offering a bit less protection is the Incipio Feather case. The case is easy to put on and take off, an important consideration for anyone planning on using the OEM car dock and/or OEM desktop dock that utilize the charging pins on the right side of the phone. The case is grippy as well and fits the phone perfectly. It has wide open cutouts that allow direct access to the phone's volume and on/off buttons without interference. I read that some people modified their cutouts, but this must have been for an earlier version. The one I have needs no modification as the cut outs are well designed and large. The case wraps around the back and sides and edges of the phone but leaves the top and bottom edge exposed. While it doesn't cover the entire phone like the NGP, the trade off is that it is extremely light and adds very little to the phone's girth. I purchased my Feather case on Amazon for around $11. I've seen other posts about people complaining that the Feather doesn't provide sufficient protection. I guess these folks didn't bother to read the advertising first. This case is for people looking to enhance grip and protect the phone from scratches. If you're a brick mason, a heavy machine operator or are just rough on your phones, get something else, like the Incipio Silicrylic.
I don't own a Silicrylic so I can't comment on it other than to say that from the literature, it appears designed to provide maximum protection to the phone. It is a two piece case with a polycarbonate shell and a silicone core.
One nice thing is that all these Incipio cases come with a high quality dry screen protector.
