I've got it installed from Windows Store on Surface RT (takes quite a while to install - your download time may vary) - here's what I've noticed:
1. Yes - you get Outlook. Works like on the desktop. Love it!
2. You get new tile sizes on the Start menu and you also have the option to add an extra row of tiles and use wallpaper as background for Start menu.
3. Split view is nice to have 2 apps running side-by-side and the size is variable. Does NOT work for all apps.
4. Jail break does not work.
5. I noticed the installation leaves a "windows.old" folder - not sure whether to delete it or not.
6. Am curious if I can "reset" and get back to Windows 8. Haven't tried it yet but read somewhere that you can't downgrade on Windows 8.1.
7. Some tweaks to Internet Explorer - such as improved but not perfect bookmarks. Not revolutionary but fine.
8. Previously working wireless HP printer does not work anymore.
9. Expanded "PC Settings" menus to include more of the Control Panel items.
10. Start menu. Applause (?). Pretty worthless.
11. Several new apps - scan, health, cooking, calculator, alarms, sound recorder.
I'm sure others will post more.