Been on OS X 10.10 since DP1 and this update addresses so much of what was 'wrong' with the beta if you could say that
Full Exchange is finally working
Safari tabs work
Safari opens URL's within an AD environment now
Its quick and fluid
It really is much smoother than DP3. No more stuttering when opening NC. Some animations still need tweaking, but it's getting there.
Notification Center (NC)
Ahh, fair enough. How are the Mission Control animations?
DP4 is still crashing Safari tabs for me left and right. Also now other apps are crashing a lot (i.e. Sublime Text). So far I haven't noticed any improvements in stability from one DP to the next.
Speed is better though. Animations are better. And indexing hasn't been as bad.
Exchange support for one of my Exchange accounts is working better but not perfectly. The other account still is a mess (emails not syncing) but it has 60,000+ emails in the Inbox.
Have you tried fixing your disk permissions? Some people were having Safari issues and this fixed it for them.
No, I haven't spent much time on the forums lately. I'll give that a try though, thanks!