Depends mostly on what you classify as a "proper" Steemit mobile app.

As for smoothness, fastest, user-friendly and being slick, the Partiko Mobile App is already a proper Steem mobile app. Basically, it's quite good for browsing, commenting, upvoting posts made on the blockchain.

However, with it being a mobile app the app itself lacks some functionalities that can only be found via the web. Features such as "sending steem, delegating, changing profile info and picture" are still lacking on the Partiko app but I myself already consider it a "proper" Steem mobile app as I don't really care that much doing transactions when on mobile.

There are of course already the eSteem app which I heard can do these things.  So yeah, it's just mostly depends on what you consider as a "proper" mobile app. :)