Virtually all of the criticism this movie gets, while maybe fair (in some cases), boils down to studio interference. This movie may not be the perfect send off of the X-Men franchise, but it's a solid addition to the universe. With no chance of the sinister mouse releasing any thing remotely close a director's cut, there is absolutely no better way to watch Dark Phoenix than Bobson Dugnutt's Cosmic Cut. While the added scenes don't jurastically change the movie, they sure let the film breathe a little.
As a big fan of the X-Men First Class series I thoroughly enjoyed this edit. With so little extra footage to work with, it should noted that this edit only adds a little, but it goes a long way to enhance engagement with the characters' emotional arcs and to improve the break-neck pace of the theatrical edition. The Theatrical cut I feel lost a lot of its punch by rarely allowing the characters to grapple with or react to the things going on. The ending of this film remains, for me, its weakest point, failing to adequately conclude the series, purely because its so rushed. But the addition of Charles speech at Raven's grave does a lot to round out his character arc and make the film feel like more of a conclusion.
On a technical level a couple of the added scenes were noticeable by visual transitions that felt slightly off. I even think I noticed a frame jump at one point. But generally the new scenes are very well integrated and fit naturally in with the film. The deleted scenes audio is different to the main film however, and the difference meant I had to turn down the volume every time a deleted scene came on.
If, like me, you're a fan of these characters I'd recommend this for its added value. But if you weren't pleased with DP in theaters you'll find little more satisfaction here.