We are working on a 64 Bot version, which will be released after version 11.0 later this year. At the moment you will indeed need to install a 32 Bit Oracle Client on a 64 Bit OS.
This is good to hear. Being forced to use a 32-bit client forces us to develop 32-bit in Visual Studio... including the need to run IIS in classic mode, and other hoops. Thanks.
That's strange. What's preventing you from having two Oracle Clients (32 and 64 bit) on one machine and using 32 bit one for PL/SQL Developer and 64 bit for VS and IIS?