I've watched it - it's the same cut they showed to the producers that made them decide to shoot additional scenes a few months ago, so the theatrical cut will be about 10-15 minutes longer than the "workprint."
The majority of the effects aren't finished (which makes watching the climax pretty funny, since it's VERY CG-heavy), the sound effects are all temporary (editor's scratch mix before it's sent off to the sound designer and sound mixers), and the music is all temporary (the film hadn't been scored yet). The credits are also roughly thrown-together, then there's a mid-credits sequence, then they use the credits form X-Men 3 in their entirety before going to a post-credits sequence.
In general, the movie would be on par with "The Last Stand" if they hadn't completely ruined the characters of Gambit and Deadpool. I don't think the additional 10 minutes can possibly save it.
Note that I never intended to pay for this film in the first place, and the only reason I watched it was because, as an editing student, work-in-progress cuts are very intriguing to me. Watching this workprint was almost as educational as my classes, unfinished though it may be.