It might be more efficient than full-on 64 bit programs as long as a single proc...

It might be more efficient than full-on 64 bit programs as long as a single process is ok with <4gb ram.

Debian has some work in progress on a port to x32 here: https://wiki.debian.org/X32Port

But it looks like they had the foresight to disable it for regular kernels because of security concerns: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=708070#10