Post #3 will be continually updated
OP wasn't getting everything in the thread, so I've complied a list of everything in this thread (I think). It doesn't include:
- big features shown on the Yosemite Preview on Apple.com, or the Keynote
- bugs
- Things that haven't changed since 10.9
- Anything relating to third party software.
Wanted to link to the user that had noted each change, but too time consuming. Have linked back to the thread for Pics.
General
- boot screen is now the same as iOS: black background, white apple, thin loading bar
Pic
- login screen is your desktop Picture blurred, instead of black background.
- When you set up your Mac you can set it up to sign in with your Apple ID.
- Lock screen/login screen Pic
- Full Trash image
Pic
Apps [Alphabetical]
Calculator
- Has new icon, but App looks the same
Pic
Calendar
- Preferences are the same except Advanced is now on the far right. Also has option for overlay Calendar: Chinese, Hebrew or Islam.
Pic
Dock
- No 3D dock available
Game Center
- Plain iOS 7 style look
Pic
iBooks
- Pics of the new look
Pic
iTunes
- No new version yet.
Mail
- Other than new look and new features demoed at the Keynote, no difference expect option to display short names/nicknames
Maps
- same slightly changed icon
Mission Control
- New Look
Pic
Notes
- v3.Paper side is lighter, new note and share buttons are at the top.
Pic
Photo Booth
- Not included in DP1
Preview
- Can sign your signature with the trackpad
Pic
Reminders
- iOS 7 style look:
Pic
- you can do the last monday of each monday, 5 days before the end of the month etc.
Pic
Spotlight
- Currency Exchange
Pic
- Holding down Command while selecting something in Spotlight shows its file path
Pic
- Can browse the OS Structure
Pic
System Preferences
- Extensions points you to the Mac App Store, they're for the share menu and notification center
QuickTime Player
- You can plug in an iOS 8 device and record audio and video.
Utilities
- Activity Monitor changes:
There is now a Compressed Memory column you can add to Activity Monitor.
Instead of unclear "Safari Web Content" processes, Activity Monitor now shows the full webpage url of the Safari Web Content so it's easier to see which webpage is taking the most amount of memory.