A couple of years ago Spotify rewrote their clients to use CEF (Chromium Embedded Framework), so since then their clients are in some sense native and in some sense not, and much more consistent across platforms.

Anyway, I agree with you that they have been pushing the envelope in terms of mobile functionality, especially iOS. Lately I'm not happy with how Android has crippled their lock screen experience by screwing up the lock screen widget API - but that's not Spotify's fault.

To any Spotify skeptics, I highly recommend trying the premium service. The social feed, cross-device sync, BPM matching for runners, collaborative playlists, Spotify Connect (ability to switch and control music playing on another device), Algoriddm Djay integration, all changed the way I experience music. Their radio/suggestions engine is not as good as Pandora's, but is slowly improving. The only thing that is sort of a letdown is the visualizations API, but I can see why it's not a priority.