Honestly, I could only remember 1 group from the 2nd bracket of The Sing-Off, other than the two teams which were eliminated that's how little impression they made as a whole. I went back and skimmed through the episode again to refresh my memory and I have 2 groups I like. Unfortunately, one of them doesn't have a snowball's chance in hell and that's North Shore, the older guys doing do-wop. I <3 do-wop and their rendition of Run Around Sue was fantastic. The problem is I'm not sure they'll have the versatility to really get very far. They'll end up having to convert pop songs to a do-wop format and that might be pretty problematic for them. The other group I really like and think has a good chance is Pentatonix.
As far as I'm concerned, everyone else in the 2nd bracket is just fodder and can go any time. Maybe my impression will change after the new episode tomorrow but it certainly wasn't a good first impression and as their signature song, you'd think it was the best they had to offer. Still, it's not unknown for groups to get better as they go. One clear example of that that springs to my mind is The Backbeats from last season. I thought they were roadkill but they managed to keep stepping it up a notch. Only time will tell if that's something the other groups this time around can match.