The Windows 8 and Windows RT version of the Skype app has been updated. The latest version has improved control over your contacts including the option to block and performance improvements. The last few updates of the Windows Store Skype app have made the app perform much better.
The app is free in the Windows Store.
Release notes
RT @isdixon: TDL Post: Skype for Windows 8 and Windows RT updated: http://t.co/hnhHCREMIA