That art style. That's what really sold me on this. Man, those colours! And the character design's pretty good, too, judging by the trailer. It's a Monty Oum production, as well, so obviously the animation'll be great.
That leaves the writing and acting. If they're any good, I'll probably have a new favourite web series. If not, I'll be disappointed. This is what'll make or break the series. It's got so many good points already, but if the story's an incomprehensible mess, then it's all for naught. Even if the dialogue's good, it'll need a decent story to hold it together. However, without decent acting, the dialogue won't sell. If they get this wrong, it'll ruin the production.
I'm still REALLY looking forward to this, though. Even with the possibility of horrid writing and acting, I really don't think they'll screw it up. Rooster Teeth has a good reputation for high-quality productions, and even if it's more a Monty Oum production than a Rooster Teeth one, I don't think they'd host something they think might be bad.