First, let me just say, the Overwatch cinematic trailer is so good, and I'm glad (if I'm not mistaken) that they're going to continue making more moving forward. The style just reminds me so much of Pixar which makes it a blast to watch. (I can definitely imagine it being a decent TV show or movie)
Anyways, never was a big fan of Team Fortress honestly, simply couldn't get into it. The combat and classes felt kind of dull... but then again, that's just me.
And despite it's similarities to it (I've also heard it being called a "clone/copy" of Destiny and Dota amoung other things but those claims are rather silly!), Overwatch kind of caught my attention. The fast gameplay and the uniqueness that each separate character has compared to the others seems like it would make like a fun time.
I'm especially a fan of Mercy, Zenyatta, and Bastion at the moment, all seem rather run to play as. There's also quite a few interesting ones in the various trailers/posters for it, like the Clint Eastwood looking cowboy or the roller skater holding what looks like a mini flood-light... I'm certain they could add quite a few interesting characters as they progress.
It looks good, hopefully it pans out rather well in the end. But at least so far I've heard it's gotten rather good comments by those who played it back during Blizzcon.