That "The 100", even if it had its share of shortcomings, didn't seem to take the easy way, was easy to see from early on. Jaha's son's death at the beginning of the series, or Finn's one in the middle of the second season showed that "The 100" was not afraid of taking decisions, even if they were the wrong ones.
For some viewers, what happens in this episode will leave them baffled and/or angry. Because it's not what one expects of the showdown between the Ark-Grounders vs Mount Weather. Is it a good decision? Let's see. For now it's more than a worthwhile one.
"The 100" falls on one of the problems that serialized series usually have: the need to keep things going. So it takes a cheap decision. Not bad, but cheap. It has taken a couple from the beginning till now. But this one is probably the biggest.
The episode is centered around the last big battle, with the Mount Weather surrounded, with four teams against them (taking into account man-army Bellamy on the inside, who is supposed to get the caged Grounders on his side). Both groups will try to do anything but anything for theirs, and save their lives. It does for good TV, and as said above, for a strange twist, that, nonetheless, makes sense. The atmosphere is great, the action restless, and the characters all have their moments.
It's uneven, and rushed, but not a bad episode. It's surprising, and gut-wrenching, and nail-biting, that's for sure, and that makes for any shortcomings it may have.