There are no new features in this release. This is a maintenance release, which resolves a list of issue present in previous releases. A list of resolved issues can be found in the changelog.
Note added Nov 4, 2013: We found a problem with the binaries of build 64 and have corrected this with Build 65. There is no difference in the source code so these two have exactly the same version (4.11), the build number is the only distinction between the two. If you have found problems importing SBML with Build 64 then please upgrade to Build 65! If you have not yet downloaded, then just use Build 65.