I have been using SharePoint Workspace to keep an offline copy of my MOSS document libraries, since there are many situations where i want the documents and i may not have an available connection.
After recently upgrading my PC to Windows 8 (that's another tale!), I also upgraded to Office 2013. When upgrading i had removed my previous Office 2010 install, and was surprised to find that SharePoint Workspace was no more.
Reading up on this some links i found that Microsoft has finally moved out the last remaining client based on the Groove product for peer to peer file sharing and collaboration. The first solution was to have Office 2010 to continue to coexist and use the Workspace product with Office 2010.
However reading a bit more, i found that the ability to sync with a remote document library is possible with the SkyDrive Pro, and you use Windows Explorer rather than a separate client for file browsing and managing.
The new feature seems to be working fine for now, will update more as i use it further.
Some links:
http://www.jasperoosterveld.com/2012/09/office-2013-sharepoint-workspace-is-no.html
http://social.technet.microsoft.com/Forums/en-US/grooveserveritpro/thread/0508d418-7cc2-40c0-8914-b863bf5e6892/
