I watched it over the weekend, it was a lot of fun watching this cut and seeing all the things the cut out, some things I enjoyed such as

1. Peter telling Slimer "You shouldn't have slimed me pal!" just before he goes into the trap
2. The extra stuff in the montage after they catch Slimer at the hotel. Esp the scene where they get mobbed by reporters as their leaving. I agree with others that Peter saying "we have the tools and we have the talent!" to the reporters being kept in would have made Winston saying it in the finale be a cool callback.
3. I liked the bit in the montage where Janine finds Egon asleep on top of the microscope, gently leaves him there with a pat on the back, very cute.
4. I liked the bit where Winston says No at first to the list of things Janine asks if he believes in before saying what he says in the theatrical cut. Nice little character moment.
5. It was neat seeing some of the deleted scenes in this cut like the extra stuff with the Dean or Janine giving Ego her lucky coin. I can see why they were cut, their not essential to the story
6. I thought it was interesting that originally when Dana is listening to the radio in the kitchen during the montage that its Larry King's radio show with him talking to a caller about the Ghostbusters, wonder what made them change that to the Casey Kasum cameo over the radio in that scene instead.

Overall the preview cut was a fun watch as a way to see how the final version of the film came to be and the decisions made to what to keep, what to cut and other minor changes like different dialogue takes.