There were quite some workarounds floating around to make it work. Having to install a 32bit JDK on a 64bit OS for a 32bit Java application always seemed weird to me. So I'm glad Oracle finally got around the bend and provide a fully functional SQL Developer for Windows x64.
Of course the language / regional fix still applies to this version, as they didn't bother to include a GUI option to specify them. In case you are wondering why your SQL Developer shows up in some weird language other than English, add these lines to your sqldeveloper/bin/sqldeveloper.conf: