Ever since watching the announcement trailer for Blizzard's TF2 clone, I've wanted to know more about how one of its more interesting characters works. Just uploaded today on Overwatch's Youtube channel, we have some raw gameplay from the Scout *ahem* I mean Tracer.
In addition to showing the Tracer, it shows what it's like to play against a Tracer — though the player in the below video doesn't seem to have too much of a problem with the fast-moving assassin.
The "rewind" ability seems to be tied to the forward dash, instead of just independently rewinding anything. There are a few points when the player uses this to dash forward, drop a grenade, and rewind back out. It looks like rewinding out of a dangerous situation you dashed into will be a standard move, and at around 2:30, the player does this while dashing through an enemy shield.
In addition to looking a bit squishy, the Tracer seems to be balanced out by having a criminally low clip size. That said, if you're nabbing the headshots like this player is, it seems like even the big tough enemies don't take too much persuading to go down.