I am.
Now, if we were talking about a video game, or an anime, or even something from the lighter end of Fantasy (LotR, Princess Bride, what have you), I might not mind.
Thing is, GoT is in a sort of... historical fantasy/magical realism subgenre. Outside of the plainly magical elements, everything else should be historically accurate. And to put it simply, never in history did anyone (or at least, not anyone with training) fight by flailing two longswords around in a circle.
Has dual-wielding occurred in history? Sure. But the thing about real-life dual-wielding is that it requires blades of different length. In Medieval Europe, maybe a shortsword and a dagger. In the renaissance you'd more likely see something like two different lengths of epee. In Japan they would occasionally go Katana/Wakizashi.
Look at The First Law: there we have duelling steels, expressly describes as two thin, light, agile blades of differing length, with different functions. That's a realistic depiction of dual-wielding. What we saw in the trailer is just... ridiculous.