The Teen storyline just bothers me. It's like "The Gates," an otherwise solid premise but suffers the 1/3 of the episode that deals with stupid teenagers doing really stupid things and acting overly dramatic. At least the Pilot was horrendous with that, the whole "I hate you for protecting my sister" and then running into the dinosaur-infested jungle when you have NO clue what you're doing. The subsequent episodes' teen storylines weren't AS bad though.
As for someone complaining about the "cliche" Sixer storyline, it's one of the few interesting things about the show now. It's mysterious, like the whole "The Others" bit on Lost towards the beginning/middle of the show. Then again, we haven't seen much of them / that so it's possible that part will stink.
It's still... alright in my book. Not as great as I was hoping, but not too bad. For 8PM on a Monday the only other contender for my attention is "How I Met Your Mother" which I haven't liked as much as I used to lately.