Also, I have similar requirements as you (mostly want to play media off my NAS through XBMC or any other player with sufficient format support), but I want to use a remote rather than mouse and keyboard - is this possible with the Nexus Player or is there another good solution for this?
My first generation Pi was significantly slower at Kodi (things like menu traversal, library updates, API consumption, etc) than a second generation Pi (I tried a friend's). So I was already considering $35-40 for a new Pi when I saw the sale price on the Nexus Player. But the bigger deal for me was Google Cast support. I wanted a single device that could run Kodi and also that the family could cast Youtube, Soundcloud, etc using phones.
Regarding remote - the Nexus Player comes with a simple, bluetooth remote (as does the Shield TV now apparently). It works great for simple Kodi interactions but doesn't work for everything (the biggest one that I've noticed so far is the lack of a context button). But as thoughtpalette mentions - I use Android and iOS remote apps when I need more control over Kodi (Yatse is what I use on Android). Also there is an Android TV control app for Android phones that has the same buttons as the simple Nexus Player bluetooth remote.
Also, I have similar requirements as you (mostly want to play media off my NAS through XBMC or any other player with sufficient format support), but I want to use a remote rather than mouse and keyboard - is this possible with the Nexus Player or is there another good solution for this?