Not really worth it in my opinion. The challenges feel like an afterthough that was made by giving an intern access to the map editor for a couple of hours, and in my opinion, this should be part of the base game. Releasing this as paid DLC just feels like a greedy moneygrab in order to squeeze as much money as possible from fans of the series.
Can't really recommend this unless you've already 100% completed the game and just want more (or a challenge), in which case, get it on sale, as I can't really recommend this at full price to anyone.