Sym is great for low HP kills (set up sentries at common health packs) and giving you a heads up for when you're being flanked if you spread her sentries around common flank routes. If you're in a team that communicates, this can be amazing.
Her weapon is... Probably the one that needs the most skill out off all the LMB/RMB besides maybe Tracer. She can be an absolute terror if you charge up her RMB, pop out from behind a wall, hit someone running at you / close to you, then finish them quickly with LMB. Pretty much insta-kill for all non-tank type heros. Just running around holding LMB... You're probably gonna have a bad time.
Also, her RMB shoots through Reinhardt shield, so that can be useful on chokepoint maps like Anubis since you can wall peek and spam her charged RMB to help counter the shield. Also a great trick for when the match just starts and everyone is running out of spawn since a well timed sym orb can go through the gates just as they're opening and everyone is hiding behind reinhardt's shield (which may or may not be deployed, but even if he deploys upon door open it won't help
)
Mix all these with good teleporter placement and you have a great hero.
Miss any of these elements, Symmetra is gonna suck for you.
I suppose there's also the argument about super high-end play viability... And in that, she's out of the meta currently. A lot of the tricks and tactics Symmetra uses rely on playing against average or lower foes (Circling the payload in a 1v1 dropping sentries when you break LoS doesn't work as well against high skill players who can flick to the turret then back to you in milliseconds as it does v.s. lower skill players that might not take their aim off you for a little turret or even realize that little buzzing isn't your LMB) and is heavily countered by enemy team communication and co-ordination, so yeah.
This post was edited by Dragonkilla8 on Aug 9 2016 02:00am