As you have seen already Search in SharePoint 2013 Preview has been released. Check out the page : http://msdn.microsoft.com/en-us/library/jj163951(v=office.15).aspx  for more details.

 

There are plenty of new things for developers like Query Web Service deprecation, REST support, SQL syntax support removed, KQL enhancements, Search CSOM etc...

 

I'm looking forward to see how developers would embrace building Apps for SharePoint around Search.