If it comes to the UK I might give it a try if the catalogue is up to scratch. I have spotify premium right now, and while I love the service the Android app is pretty shoddy. It has improved but it has a lot of bugs and despite many people complaining on their forums they never get acknowledged by Spotify. I will bravely assume that Samsung are promoting an app which works properly on their devices and give it a go!
On my S4 Spotify has the following "unexpected features":
-It often plays the same song multiple times in a row when on shuffle mode (and no I don't have repeat on!).
-It sometimes just stops playing one or two songs into a playlist. Restarting will play another song and then it stops again. You have to force close it to get it to play continuously.
-The lock screen play controls disappear and reappear at random.
-The equalizer randomly stops working until you open the settings menu again. Then the app seems to "remember" it is supposed to be on! This is so annoying I gave up and disabled it.
-Periodically it will just completely refuse to start playing anything. Force closing and restarting it offline with airplane mode disabled is the only fix I've found.