Reason being MS is rolling back that driver to their own custom version. Which engineers said is supposedly optimized for battery life and bus speed. if you want to stay on the latest driver, check out my thread called Intel released updated graphics drivers. It details there how to cut off automatic updating and keep your generic driver install that enables the Intel graphics control panel.
One thing I found is after 8.1 my machine desktop performance was set to custom and on very low, so the animated backgrounds never worked nor did I have the little animated window flip when swiping in from the right.
My last issue is the slow search as I type in the charm bar and the keyboard locking as I type. Seems a user specific issue though as logging onto my surface using a local account this goes away.
So I was having the same sleep issues with 2 Toshiba laptops after running the 8.1 update. Ran this Reg edit mentioned above to require the password when the display turns off or sleeps. Naturally this did nothing for the sleep issues, then I read on eightforums.com about disabling the Ethernet adapter restarted and both the laptops feel into a sound sleep.
Ah, but alas my beloved SP doesn't have one of these blasted adapters to disable. Kept reading and there it was, I had to leave home. Well, I had to leave the homegroup anyway. I checked with the other 2 laptops and both were not in a home group. So now the family sleeps well.
Ever since I updated to 8.1 when I run the mail app or the calendar app I get a red screen that says "switch to a Microsoft account on this PC." Its a prompt to set up various things to sync with a Microsoft account. I don't have a Microsoft email account that I use for anything other than the app store. The options for this screen are next and cancel. If I cancel I just get the screen next time. if I unselect all the boxes and hit next it prompts me to enter my email and password to log in or to create an account. I don't want any Microsoft account connection to this device but I can't seem to figure out how to stop this screen from coming back.
Ok... I've kept Office 2003 (partly because I like the three licenses included in the Home/Student version, but mostly because the 99.00 version of Office 2013 does not include Outlook). Once upgraded to Win 8.1, Outlook (when using Word as an editor) no longer allows one to select an auto suggested email address- it makes recommendations, but they can't be chosen. As a work around I've disabled Word as an Outlook editor.