8/1/13 Update: Exchange Team blog post added: http://blogs.technet.com/b/exchange/archive/2013/07/29/now-available-updated-release-of-exchange-2013-rtm-cu2.aspx
The 1st release of CU2 was posted on 7/9/2013 and on 7/12 Microsoft posted that there was an issue where Public Folder permissions were lost when a Public Folder mailbox was moved. I posted about it on 7/12 also, once it was made public, here: https://blog.jasonsherry.net/2013/07/12/dont-move-your-pf-mailbox-exchange-2013-cu2/
CU2v2 fixes this issue with Public Folders, I think this might be the only issue that it fixes. CU2 redux is not officially be called CU2v2 it seems, but the download file is KB2859928-x64-v2.exe and in the past five or so re-releases they have been called v2/v3 so I’m sure everyone will be calling this CU2v2.
Like CU1 and CU2, CU2 build 712.024 is a full download and “upgrade”, so there is no uninstall. You CAN install CU2v2 over RTM, RTM CU1, RTM CU2 (build 712.022).
Even if you aren’t using Public Folders in 2013 you still need to upgrade to CU2V2 since future security updates and IUs will be based on CU2v2.
I’m also tracking known issues (those that I know of at least) with Exchange 2013 CU2 here: https://blog.jasonsherry.net/2013/07/09/exchange-2013-rtm-cu2-released/