Well I ended up getting it, put in about 15 hours and it's been a lot of fun. Don't know how much longevity it will have - as it is obviously there's nothing really to work towards to unlock, only three game modes, and a handful of maps. But Blizzard are probably the best at keeping a game fresh for years, so I'm sure Overwatch will be no different.
The characters are awesome. They all have distinct character and voices, all have great art, and they are mostly all balanced and fun to play. The diverseness of the line up really makes it interesting, as no character really plays like any other. Typical Blizzard levels of polish on the great art, sound, music, etc. Solid mechanics and level design. This is especially true as certain characters can reach higher places, even make their way over buildings.
There are things that amaze me though - in every pvp games I've played, camping and especially spawncamping is the lowest of the low. I've seen players get tk'ed for spawncamping, but in Overwatch it's just part of the game for defense teams to rush the enemys spawn and fight them right as they exit. And characters like Bastian are pretty much designed for camping. A lot of matches seem to end up with one team camping a position, and the other trying to break through.
TBH though it does feel like a 'casual' shooter. I'm not mlg 360 noscope or anything - probably below average to be fair, but having all enemy characters highlighted in red boxes, the teamsight of enemy troops, eh, not a fan. That's not even taking into account the wallhack and aimbot abilities Widowmaker and Soldier 76 have.