I haven't had time to play OW too 'in-depth' yet but I'm around 5 hours in so this will be more of a 'first impressions'.
It's a great idea to combine Arena Shooter frenzy with the adaptability and roles that take more from MOBA elements.
I've played all the classes at least once and already found a few play-styles I can get behind. With a nice variety of game modes and maps in addition with a good pool of classes for each of the four roles offered, OverWatch achieves that "Something for everyone" level of accessibility that Blizzard had with their previous MOBA/Brawler Outing ; Heroes of The Storm.
TLDR; What if HOTS and TF2 had a baby?