For me it was the saving time. Without skoormits cleanup scripts the save file size bloats incredibly quickly which balloons save times.
I think some aspects of this are going to get fixed for 3.0.0 since a large part of it is old mass driver entries not getting purged properly but it still takes a short moment.
But yeah performance is definitely in a much better space. What slows down games more than anything is NPRs getting into combat and forcing increments down to a crawl.