Window 8.1 booting for 4 minutes. My answer
Do not enable auto update when upgrading to 8.1.
Keep it off and reboot a few times and you will see every thing is fine.
Once you manually begin to do updates you will find things are not right on the updates.
In the end once you load the first three updates you will see the lag on boot up.
Microsoft has hosed the updates some how.