I've been trying it for roughly the last month. I have run into a few quirks, for example it uses non-blocking i/o for things with libuv (for stdin), which can interfere with parent processes that expect blocking i/o. If you file a bug report, the issue usually gets fixed quickly.

I've kept vim installed as a fallback so I can easily use vim if I run into anything that is a show-stopper, at least until it's fixed in nvim. I still plan on submitting patches to both for the foreseeable future though.