I wont say I didnt love the hell out of the first half but...There were massive problems with that show...
First off, they completely ignored half the fighting that the show was capable of. It's a shame because that was what carried the show.
Second, because they tried to cram what could very easily be 3 seasons worth of content into 1 season (at the very least 2), they forced the show to accelerate itself. barely recognizing some floors and flat out skipping over dozens of other floors. Going back to the first point, the fighting is what carried the show so well and a large portion of that was the boss fights which they had far too few of. There was so much they could have done with the fighting if they just stopped and took the time to show it. Entire portions of the show were simply cut out. From a marketing stand point it was a terrible idea.
Don't get me wrong here, I'm not saying they should have turned it into the next one peice/bleach/fairy tail/naruto, I'm just saying the world that they tried so damn hard to create has gigantic holes that content just magically disappeared into. Not to mention its rather jarring to see them fight one boss and nearly get eaten alive by it and then all the sudden appear in the next ep 10 floors past the one they struggled so hard to get to without anyone of importance being gone.
Third. It goes without saying but ill say it anyway. The second half should have been another season... period...
Everyone i've talked to about it agrees to some extent. the second half took away from the first half and quite frankly it was just a long winded way to wrap up the show. There was another show famous for doing this... it was called dragon ball z, you remember right? the show were it took an entire season worth of content just to kill off the main enemy's HENCHMEN?!?!
sidenote: I'm not even gonna get into the creepy inter-family love non-sense that they threw in there because they felt like they just needed "something" after throwing so much down the drain....