The learning curve is very steep. I'm still learning how to play it after 1+ years with it. For me, the big deal is that it is a new genre (for me) and I also love that it forces teamwork and strategy with players that play a 'support' role which their sole goal is to help a 'carry' win his lane. Check out highlights of Dendi from Navi in Dota 2 International 2013.

It's basically a game of chess.