64-bit binaries net me a 15% performance increase with my application. Obviously it can vary per application, and depends on where the bottlenecks are. It's been my experience that x86->amd64 is often beneficial: the x86 is so register starved that it makes up for the larger pointers, and most of the latter is mitigated through 32-bit relative instructions. Now PowerPC, sure. 32-bit PPC code does tend to run faster than 64-bit from my experience.

The other advantage is being able to utilize more than 2GB of memory per process. The reason to favor pure 64-bit is to get rid of all that extra 32-bit compatibility code. WoW64, in this case, or ia32libs on Linux.

Whether you're pragmatic about it or not, 32-bit will eventually go away. I'd prefer to see it sooner rather than for it to drag on for decades like IPv6.

And yeah, WoW64 is a clusterfuck. Basically, Microsoft wanted to make porting 32-bit applications as easy as possible. Since some applications may have been hardcoded to System32, they stuck the 64-bit libraries there, and put the 32-bit ones in WoW64. They also cloned the registry so you actually have 32-bit and 64-bit keys (see KEY_WOW64_32KEY flag.) What can I say? Microsoft's always had a thing for rigid backward compatibility at the expense of common sense design. But they are still the market leader, so I guess they know a thing or two :/

I don't care for your Firefox example. What if one single tab needs >2GB, like say a really high-end WebGL game? What about other applications? People found similar tricks for getting more memory in 16-bit processes too (far pointers), but we aren't still using Win16.

I'm accusing people of apathy because they resist change simply because it's change. I get being pragmatic, but at some point we have to cut ties with the past. Even Microsoft understands this, as you can no longer run 16-bit applications on the latest versions of Windows.

No doubts about the advantages of x86_64, I would insist on it in a new computer for virtualisation and encoding DVDs. But many people don't do much more on their computers than they can do on their highly restricted armv7 gadgets. Desktop software has reached a plateau IMHO, I don't think we can extrapolate from the 16->32 bit change. Gamers and IT professionals are a completely different beast of course.

How do you know that people hate change? Has anyone ever said "no, I don't want to run a 64-bit program, I've always been a 32-bit person"? People have to endure the crap in my grandparent post and that is what they hate and resist, especially if there is no tangible benefit to it. SSDs have entered the mainstream market much later and I have seen nothing but praise for them. SSDs are change too, often a painful one for a running system, but they solve an obvious problem.