> you happily run 32 bit userspace on a 64 bit kernel, you already don't have to care about this.
I do have to care about it if, in the future, I want to run a application that benefits from 64bit-ness.
Some operations are faster in 64bit and many applications, such as games, already benefit from the larger address space.
> (it may help if your libraries were all fat, but I fail to see how that's really much better than having /lib32 /lib64 (your hard drive may be large enough to double the size of everything stored on it, but mine sure isn't)
Yes. That is what I am talking about. Getting rid of architecture-specific directories and going with FatElf for everything.
Your wrong in thinking that having 64bit and 32bit support in a binary means that your doubling your system's footprint. Generally speaking the architectural-specific files in a software package is small compared to the overall size of the application. Most ELF files are only a few K big. Only rarely do they get up past a half a dozen MB.
My user directory is about 4.1GB large. Adding Fatelf support for 32bit/64bit applications would probably only plump it up a 400-600 MB or so..