I love this feature. It was actually one of the reasons I switched over from the OUYA (that, and the hope of improved performance, under the pretense that the games I played would actually be available on this platform, but I don't want to get off topic).
I still send YouTube videos to Kodi rather than casting them, but it's very handy when other people come over, that they can simply push media to my TV without needing some special app or setup. The OUYA could do this for a short time thanks to CheapCast, but Google blocked that in most apps.
A nice tip, if you were not aware, many videos from webpages can be casted via Chromecast if you are on Firefox (not sure if Chrome can do this). It's sometimes nice to just pull them up from a browser rather than installing another app for another website. Or you can cast your whole screen, but it's usually a bit laggy.