I'll explain how it interacts with my Smart Playlists.
I have playlists like this:-
These playlists are available in Marvis. When I play a song and then sync back to iTunes it updates the 'Last Played' date and the play count. It does
not live update the Smart Playlist from within Marvis.
I have found a work around though. If I want to update the Smart Playlist I force close Marvis (swipe up), open iOS Music Player which updates the Playlist, re-open Marvis and voila all fixed. Yes it's cumbersome but I don't have to do it very often at all and this may get fixed in a future update.