When Arrow has its season two finale tomorrow night, a special preview of The Flash will be running alongside it (get it? GET IT?!) But you can catch your first glimpse of the Scarlet Speedster in action at the end of this promo for the episode. But blink and you'll miss it!
If this is indicative of what the super-speed effect is going to look like, I'm not 100% on it, but I still found Grant Gustin so unbelievably charming in his two-part Arrow appearance that I can handle any special effect woes.