Well I played the Open Beta, and so far I'm enjoying it! Hope to get the actual game soon when it gets released.
Though after actually playing it, my thoughts on each character have changed. Some of them work a bit differently than I had expected.
-Tracer: Well she certainly is cool with her time dash and reverse time ability (helpful in a pinch), but I really think she needs better weapons.
-Soldier76: Basic character, plays like your typical shooter. Just Assault Rifle and Sub Explosive. Aim and shoot, that's about it. Isn't too impressive to me.
-Genji: Well he's not what I expected. His Ninja Sword and Deflecting ability is actually like one of his abilities with a cooldown, his main and sub are just his Ninja Stars. I was originally thinking he'd play like a true Sword-wielding melee badass like Devil May Cry Vergil, or Roronoa Zoro, or Ryu Hayabusa, or someone like that, but turns out his abilities I'd compare more to Biometal Model P from Megaman ZX due to his are more about mobility and throwing blades instead of hacking and slashing. Nonetheless though not what I originally expected, his climbing and mobility is definitely helpful for me.
-McCree: He kinda plays to me like Soldier76 but with handguns, though my friends have found him to really be able to do some damage with him. I guess his playstyle takes some getting used to.
-Roadhog: Definitely one of my mains. His gun dishes out the hurt, and he even has a reusable health potion. Also his hook is so useful, especially for taking out Bastion in Sentry Mode, Reinhardt with his shield up, and Widowmaker. Pul them up close and finish them off.
-Junkrat: I like playing as him more than Pharah, he's better with explosives. Especially his special attack, the Wheel Bomb, that thing is as fun as hell to use. I also love using the Bear Trap a lot.
-Reinhardt: This guy I think ends up being one of the most defensive characters for me. Often times when capturing the objective I like to set up his shield and protect my allies. Also, despite how usually in these games Melee-Focused characters tend to be the worst, this guy is an exception. My only problem is that his Special Attack is hardly useful, though maybe that's just because he'd be OP otherwise.
-Bastion: Well unlike what the trailer showed, Bastion doesn't have a shield in Sentry Mode, but still, he's also just as helpful for protecting an objective as Reinhardt. I guess the shield was removed due to balance issues. And he's even got an auto-repair ability to replenish HP later. An awesome and somewhat sweet robot, no wonder I like using him.
-D.V.A: Well I kinda think her guns are OP due to having infinite ammo, but she's surprisingly mobile and tough, well except when her mech gets destroyed. I kinda hate how her special attack involves making it explode on them. Wouldn't be so much of a problem if the time it takes to get another one wasn't so long.
-Mercy: Basically the all-around Medic. Helpful in a pinch, and can even bring back recently eliminated allies. The only problem is that her actual attacks are really weak.
-Lucio: I really like playing as this guy. He's one of the better supporters who can also fend for himself, and I love his special attack.
-Pharah: Rocket wielding woman with a jetpack. Her rockets have good blast radius but I find Junkrat to be the better explosives user.
-Mei: Wouldn't recommend. She really doesn't work so well for me, though I guess it just takes some time to get used to. Most times her freezing ability hardly helps. Nevermind, finally got the hang of her in the last two days. Her Freeze Ray is best used when you've got others backing you up, or are one-on-one. She's easily taken out by large groups, but one-on-one is easy due to the freeze. Also try to hold off Tanks with your Ice Walls, instead of freeze them.
-Torbjorn: Not what I expected. Though his Sentry Turrets are good at holding a point, collecting enough metal to upgrade them is not as easy as it is in, say TF2. Not to mention his special attack is hardly useful. Though he isn't as bad as, say Mei. Perhaps might need to adapt to his style.
-Widowmaker: Snipers are always useful in these sorts of games, and she has some of the better defenses like a Grappling Hook for a quick getaway. Though unfortunately, getting proper headshots in Overwatch can be tough, with stuff like D.V.A's head being positioned differently, and Bastion's not being visible while in Sentry Mode, and such. Still woudl recommend if you have a good shot.
-Symmetra: About as useful as Lucio, and better than Torbjorn. Her wall guns and teleporters are so helpful, as well as she has a piercing shot weapon, which penetrates shields too.
-Reaper: This guy is badass! Comes in without warning and wrecks havoc with dual shotguns. Plus, his special attack really gets a lot of kills for me most times.
-Hanzo: He's got the mobility of Genji but with things helpful to teammates such as arrows with tracking devices. Oh, and his special attack is one of the best in the game. No doubt about it he's awesome.
-Winston: His bubble shields and jetpack are helpful, but overall I prefer Reinhardt over him as the heavy-hitting close combat fighter.
-Zarya: I dunno but she ends up being more of support to me than Tank. I often times end up deploying shields for allies more than fighting as her. Nonetheless not bad.
-Zenyatta: Dunno why, but I really am having a hard time with him. Similar problems to what I have with Mercy.
As of now, my current mains have changed from what I've expected. My favorite ones to play as are Roadhog, Lucio, Bastion, Reinhardt, and Genji.