This is the most rewarding, frustrating, entertaining, exhilarating, maddening, complex, and complicated game ever made. It never gets old, always changing with new and exciting variables with every new match. Every teammate will have strengths and weaknesses, every draft will change and morph to better or worsen your chances of victory. Every item selection or ability build will change your odds, but ultimately your understanding of timing and mechanics will gain you an exhilarating victory. And if you ever age out of playing or decide to be more casual, then Dota 2 has an esports scene that rivals IRL sports.

PROS:
You will gain friendships that will transcend the game.
You will learn patience, forgiveness, and a deeper understanding of psychology.
You will learn real world twitch reaction geometry, and trajectory mechanics.
You will learn to calculate high level math in real time.
You will learn how to communicate with people that have different personalities and ability.
You will gain a better understanding of teamwork and synergy.
You will have more fun in a 1 hour match then a 100 hour play through of any other game.
You will save money, it's Free to Play!

CONS:
Your significant other wont understand that there is NO reasonable pause option.
Your current friends are probably too dumb or too busy to ever learn how to play.
You will have to make new friends.
You will have to manage your time or it will become an addiction.
You will spend a ton of money it's "Free to Play" not free to customize.
Finding Match times are high, and missing a queue is punishing.


Additional thoughts:
There is very little new player help, the game is so insanely complicated that new players will most likely give up or not try at all and eventually Dota 2 will be no more. The only real support comes from other players on reddit /r/DotA2 or youtube and most of the bug fixes and patches are because these communities complain so much the janitor at Valve will push a midnight update to keep reddit from burning down.

With that said, I am a 40 y/o business owner with 2 kids, a wife, and a huge family. I volunteer at a charity and work very long hours.... but when my work is done and the family is all tucked in I boot up Dotes and 5 stack with my boys to Defend the Ancient.

Dota 2 in my humble opinion is: The Greatest game ever made, period.