I have the same problem with a new ASUS X550LA laptop with an i7-4500 cpu and 8GB RAM that came with windows 8. I upgraded it to 8.1 and my new laptop now runs slower than my old HP Zv6000 with 1 GB RAM.
Further, when I upgraded from 8 to 8.1, the upgrade process wiped out (or, at least, refused to recognize my local account) so I had to create another cloud-based account (which I don't want) and then I had to jump through the hoops (again) to recreate my
local account. Isn't interesting that the install/setup process can't recognize an existing local account when it does an upgrade from 8 to 8.1, but it has no problem recognizing the "lost" local user account (e.g., Joe) when I asked it to delete the new
account with the same name (i.e. Joe) after I found both the new account and the old account in C:\Users. Yep, it deleted both C:\Users\Joe and C:\Users\Joe_000) which, obviously, made it impossible to reconnect to my original lost account and configuration
settings. Even if Microsoft has a way to reconnect to existing accounts on an upgrade, wouldn't you think that after 20+ years of doing updates that they could figure out how to do it right and not force their customers to spend endless hours redoing and
relearning the "new and improved" way of doing things?