Heroes is a show you really have to wait until the end of the season to judge. Just because something isn't explained in one episode doesn't mean that it won't be by the end. Most of the things people are calling plot holes just haven't been explained or revealed yet. I'm sure we'll find out exactly what happened when Hiro stabbed Ando. Either it was staged or he really did stab him, we'll find out why. We'll find out more details about Nikki, Tracy and Barbara as the season goes on. As of right now its obvious they were triplets that the Company experimented on and gave powers too. There's really no reason to get worked up about unresolved plots when they're not even halway into the season.