I'll give my thoughts on the cuts group by group.
Groups
To be honest with you, I really could care less about all of the groups, so I am rather impartial as to who got cut and who gets to move on to the live shows. But with that said, I would have kept "The Anser" before keeping either of the three bigger groups she kept, with the Brewer Boys being the group that I think currently has the best chance at going deep in the competition.
Boys
The boys were a tough group to cut in my opinion, because you can look at this group with so many different perspectives and come up with a different top four each time. My personal top four would have been Phillip Lomax, Nick Voss, Tim Cifers, and Marcus Canty. They took Astro (as it appears they are going to call him for the remainder of his time on the show) and Chris Rene instead of Nick Voss and Tim Cifers. I can be on board with this, but I'm just not Astro and Chris Rene can adapt enough to bring something different each week. I look forward to seeing what they can do and I can't fault Mr. Reid for his decisions regardless of the outcome.
Over 30's
I'm pretty bummed out about this group. If it was up to me, I would have kept Josh, Elaine, and Stacy for sure, with the last spot going to any of the guys BESIDES Dexter. I really can't understand her decision to keep him and I can only hope that I feel this way because the producers or mentors picked the worst song possible for him for the Judges Houses performance. But based on everything I have seen from him, he should certainly not be going through. Elaine was so good and I can't believe Dexter was put through instead of her!
Girls
Lets start with the fact that Rachel & Drew are the two best contestants in this competition so it's no surprise that they made it through (I would have stopped watching if that weren't the case).
On the other hand, Simone and Tiah are two of the worst contestants in the competition and I can't believe he put them through. Especially Simone, who put forth the least amount of effort and showed the least amount of interest in actually trying to COMPETE!
He could have easily put Melanie through in place of either of those two and saved himself the embarrassment of having to put 5 girls through to the live shows. He could have also put Tora or Jazzlyn through to round out what would have been a dream four, but now he has three great acts and two who have no business being in the live shows!