Can view and post to Instagram right from Mac's menu bar. Basically a mobile website ported as a Mac app.
No interesting features like messages or stories, but Vu is not to be blamed. Instagram does not open up API to others. Poster is similar.
I've been using Poster all these days to see Instagram posts and post on Instagram. I guess Vu is the same as Poster. I wish Instagram opens development for third-party developers and makes it possible to build more robust apps.