Earlier quoted context omitted.
I have no problems running Syntastic. What are you running in to?
That was months ago actually. I just retried and it works perfectly, but it's still synchronous and blocks the UI. This is what I expect from neovim: provide me with async lint/checks. The only ongoing works on the problem I've seen are https://github.com/scrooloose/syntastic/issues/1253 and https://github.com/benekastah/neomake , which I've not tried yet.
It would have to be written using the new remote-plugin architecture I'd think. Plugins that were written for Vim would always be synchronous.