Comparing the two cuts....a few spoilers
I just got done watching Straight Up...and wow...what a difference.
I think the first thing to address is the "new look" of the director's cut. I'm a huge fan of the original version of Payback. And to be honest, the new "colored" look of Straight Up isn't a whole lot different from the washed out look of the original cut. This is still a very, very cold looking film.
The opening scene with the "doctor" is now gone...which is too bad, because I kinda liked that opening. But it wouldn't have suited Straight Up, because that opening really isn't needed, to tell the overall story. Straight Up is all about getting Porter from the start to the end, as simply and as ruthlessly as possible. The original version has some pauses in its narrative.
The voiceover is also gone. I had some mixed feelings about this, but the voiceover suits the original cut much better than Straight Up. I really like the new soundtrack, so much that I didn't even really miss the Jimi Hendrix riff in the middle of the film where Resnick double-crosses Porter...again. Without the voiceover, certain scenes do have a little more poignancy.
Straight Up is a good subtitle to this film, because a lot of fat has been trimmed from the original cut. Porter doesn't feel nearly as touchy-feely in Straight Up. He's actually much more vicious. A little bit of extra footage has been added to the first 45 minutes of the film, but not much. The really big changes don't occur until we "meet" Bronson in Carter's office. I much prefer the more mysterious Bronson of Straight Up, than the Kris Kristofferson character.
About the ending...Straight Up's ending isn't anything earth shattering, but its a logical conclusion to the film. Porter doesn't go through nearly as much hell in Straight Up, as he does in the original cut. But then again, he doesn't have to. He gets his money and the girl...there's simply no reason to go on from there.
Straight Up is a very direct, no frills film. It's very short at only like 80-something minutes. I would really hang onto the original version of the film though, because a lot of material in that film is still worth revisiting. This is no Kingdom of Heaven director's cut...where that one was clearly much superior to the theatrical version...this is simply an alternate re-telling of the same story, and as a huge fan of the original film, I don't really consider it to be much better or much worse than the original. If you are a fan of Payback, you should definitely have Straight Up, along with the original version of the film.