It's so tough to pick out the good from the bad with this film because the script, direction and editing was so bad that every positive comes with negatives.
I liked the actors, but their relationships really weren't fully realized, or at least adequately realized.
Positive - Teller played a convincing Reed and Reed was the focal point of the movie.
Negative - having him run from the facility after seeing Ben was a bad decision.
Positive - Jordan did well with Johnny, and his strained relationship with Dr. Storm was well done.
Negative - So little was done to establish the brother/sister bond between Johnny and Sue that it took away from both characters.
Positive - Mara portrayed a smart, independent Sue.
Negative - Sue was relegated to support for most of the film (Dr. Storm's, Reed's), and she was excluded from the trip to planet zero
Positive - Bell filled the role of Ben quite well, showing at least a sense of humor before the accident and definitely someone who had Reed's back.
I also liked the design of the Thing, even though he could have used pants.
Negative - The scenes establishing the Ben/Reed friendship is mostly with the kids, so the scenes at the science fair and moving into the Baxter institute were all we had of Bell/Teller pre-accident, so it wasn't enough.
All footage of the Thing doing any damage was relegated to a conference room video until they all got to planet zero.
Positive - I actually liked the horror aspect of the trip to planet zero, and the aftermath.
Negative - The fact that the trip was spurred on by drunken postering rather than a 'we have to do this before the project is pulled' really made it a petty adventure rather than something with any purpose. Also the fact that Sue was replaced by Victor was a major issue.
This movie could have easily been salvaged if you had a competent writer who cared about the characters more than 'his vision'.