Because yes, the remote stuff -- and PlexAmp just working the same wherever I am -- is the huge part of it. Music sits on my NAS and things... just work.
I also really like how easy the caching and offline mode is, because I frequently find myself driving in areas without mobile data service. I keep a couple favorite albums downloaded to my phone, then knowing the app will cache the next ~2 albums of queued tracks generally makes it Just Work.