As most users are aware 8.1 has now been released to the general populace. If however you were running 8.1 prior to the release due to a Technet or MSDN account then do check Windows update as some updates have been released to coincide with the general availability of the RTM. One is even a 230mb 'under the hood' bag of improvements although what exactly they are I've yet to find out. Metro apps are also getting updates and if you open the Store, click the settings charm, near the top look for 'app updates' click that and then click 'check for updates'. There is around 20 updates or so..