Borderlands 2 : Ultimate Vault Hunter Upgrade Pack Review (ChaoticDerpy)
If you intend to buy this DLC on its own, I highly recommend you pay a little more to get the Borderlands 2: Game of the Year instead. It's only slightly more expensive, but it's really well worth the money you paid for, considering the amount of content you are receiving. Hence, I strongly discourage you to buy this DLC alone, if you intend to.
That being said, this DLC unlocks the UVHM difficulty. If you felt TVHM wasn't challenging enough for you, you'd be surprised by this one. The difficulty scaling is actually pretty ridiculous at first. Normally, hitting critical points would almost guarantee a trash mob's death but in UVHM, don't be too surprised if you needed several critical hits to even kill the weakest of mobs. Mobs always scale to your level so you almost always will never deal with underlevelled enemies. Slag becomes of utmost importance since without it, you will find that your enemies are more like bullet sponges than they are mobs. They also gain constant health regeneration so giving them time to hide or take cover would prolong the encounter. To compensate, you get a whole new variety of gear to collect and new level caps to gain.
Getting this DLC would make your gameplay more action-packed and engaging instead of you just steamrolling everything for having being overlevelled for the area.