Update for reference to those having issues:
Been working with 6.5 Trial for a few days now. I see no increase in save times. 100+ tracks and 10+ VSTi on 5 minute songs.
Essentially, saving is invisible on this system. I think nothing of doing a “Save As” incremental save while in record mode. Again, N6.5, Win 7 x64, 16GB, 4770K. System OS is a hard drive. Streaming drives are Samsung SSD.
Most common aspect is see for slow saving seems to be Mavericks.