Everything is running slower and is lagging now that the update has come out. I don't know why there are so many performance issues now because of the update, but in my opinion a faster and smoother program that has less features outdoes a fancy but slow program every day of the week.
Photoshop CC 2015 is running the same speed as previous versions for most users.
But do make sure you have the 2015.0.1 update installed.
We have seen slowdowns caused by corrupt fonts, corrupt OS font caches, bugs in video card drivers, bugs in third party plugins, and bugs in third party applications and utilities (like anti-virus, firewalls, etc.).