These characters are very... anatomically interesting. Sozo and I have discussed this recently, and if you measure each character, there's quite a variation in their anatomy (especially the women).
While I do think Tracer, as the de facto mascot for Overwatch, has a fantastic character design, in terms of actual gameplay she is apparently annoying as balls (and not just because of that terrible English accent...).
Players with access to the beta have come up with a variety of methods for dealing with Tracers, such as strategically placing turrets behind their active lines (since Tracer players like to attack from behind), though even these methods are limited in the face of skilled Tracer opponents. The hope is that with the addition of Mei and her ability to slow Tracer's amazing mobility, there is now finally a perfect counter to the character, though as with any evolving meta, much less for a game that is still in beta, it's hard to know for sure.