I bought the black shell after seeing that AT&T decided to ship me the free wireless plate even though I had returned my 920 and got the 820. Here are my thoughts on it so far:

The shell adds a little thickness and a tad more weight, although it seems to balance the phone (feels a bit better in-hand for some reason). As many have mentioned, the shell around the camera is raised ever so slightly which helps protect the lens. Looks wise I'd say it doesn't change it much at all unless of course you get a different color.

The wireless charging plate works as advertised. After using it a few times I realized it doesn't really add much convenience and would not have been worth an outright purchase for me personally. Nokia should have kept it simple and rather than messing with these plates they should have just offered the stand without NFC for $50.