Just downloaded it yesterday and got the hang of it in less than 24 hours. No need to shell in a lot of real world currency to be strong. Just a bit of luck and strategy will take you to the highest rank "Dragon". Being unable to rank down even if you lost all your shields makes the league matches game a bit too laid back. I'd say it is worth playing for a day but once you've reached the highest rank, finishing daily quests, crafting and trading cards is all you'll ever do.