Seriously? We've reverted to Win 3.1 days? Wow.
If you have anything overclocked and you have any problem... if that isn't the first thing you disable you don't know WTF you are doing. Disconnecting unnecessary USB devices during an OS install is just good practice.
This is not necessary unless you are having problems completing the install. I've done the upgrade to 7 machines so far and this wasn't necessary on any of them so far. I have had 1 machine seemingly "hang" during the last part of the installation, but 1 reboot brought it right back into the setup and it completed fine.