It's a double edged sword (or in this case, DLC) for me. As with anything, there are pros to this expansion - as there are cons. In this particular case, people tend to put a greater emphasis on the cons however.
Let's start with some of the pros to this expansion: It added a decent amount of additional Story content to the game in the form of the movie plot (a few hours worth), which compared to the expansion we saw in Storm 3 (one boss battle) that's quite an improvement. We also were given several new playable characters, which again, when compared to the one new character in Storm 3's expansion, is still an upgrade. We saw the return of fan favorite game modes, and other miscellaneous additions.
Now lets take a look at the cons: EVERYTHING. As a matter of fact, every pro that I listed is doubled as a con, as this expansion is nothing but a giant d*ck slap to our faces. They're charging $20 for a mere two hours or so of additional gameplay and gave us back game modes from previous titles only under this pay wall. The new characters? I hardly need to mention it by now, but they went to the effort of modeling, animating, and creating story content for MANY new characters yet they have the audacity to make them limited to the story mode? WHY? This "expansion" is an insult. It's a $20 insult. See, while the additional story content we got in Storm 3's expansion was rather short - they at least went back and revamped the cutscenes in the entire game. That made the expansion in Storm 3 worthwhile; for the (I believe it was) $15 you not only got an additional boss battle and new character, but you had a reason to replay the base game. For the enhanced visuals (which were already stunning). Where was that effort in this game? As it was Storm 4 was a HUGE disappointment for me (in regards to the story mode) because I've come to expect high-end, quality cutscenes that were proven to rival the anime at times. What did we get in the Storm 4 base game? Still f*cking images from the anime. Had this expansion reworked the HORRIBLE "cutscenes" with proper 3D animations now that the anime has caught up with the game, then I would say this is well worth the investment. But as it is the only was you're going to get any worth out of this expansion, is if you have yet to purchase Storm 4 and pick up the rebundled copy for $50 which includes the expansion and all the previous DLC packs.