Microsoft in 16 July 2012 published many articles on MSDN, and said that Sandboxed Solutions are deprecated in SharePoint 2013, I really wanted to post about it but thought I should wait for sometime..
Till I found Andrew Connell post http://www.andrewconnell.com/blog/archive/2012/07/16/understanding-sharepoint-2013-apps-aka-apps-101.aspx and in the comments as I was reading, I realized that it was good to wait as Microsoft changes lots of things from Consumer Preview edition to Beta 1 to Beta 2 if there will be 2 to RTM and so on…
But there is no bug because it is really deprecated.
Then another post from elumenotion Blog http://www.elumenotion.com/Blog/Lists/Posts/Post.aspx?ID=158 thay says:
Microsoft is deprecating Sandboxed Solutions in SharePoint 2013
This means that the functionality will still be available for use in SharePoint 2013, but primarily for backwards compatibility with existing solutions built using the sandbox solution approach.
Microsoft’s guidance is that if you are building new applications that in the past you would have deployed as sandbox solutions, you should use the new App model for those solutions instead of using sandbox solutions.
They took a similar approach in SharePoint 2010 with the STSADM command line administration tool when it was deprecated in favor of the SharePoint 2010 Management Shell and the numerous PowerShell cmdlets deployed with that tool. STSADM is still available in SharePoint 2010, but mainly just to allow for older scripts and tools that use STSADM to still function with SharePoint 2010.