I had a small laught when seeing that the UI is basically Spotify. Listening to YT music "via Spotify" is such a delightful thought.
But I will probably try it out. The YTM web interface runs like ass on my laptop (Takes about 3 seconds just to skip to the next song), so this might make the UI usable by just plain replacing it.
Personally it made me nostalgic since I left spotify a few years ago and I long for those summer nights listening to my playlists while writing and reading.