[Someone]

"It's true that (as far as I'm aware) Solaris never supported the 64-bit application on 32-bit kernel hack that OS X did"

It also is true that (as far as I am aware) Solaris never had lots of 32-bit customers running applications and drivers that neither Sun nor those customers could recompile for 64-bits.

That and the fact that some of those customers desperately wanted/needed to access more than 4 GB of memory forced Apple's hands. They had to keep the kernel 32 bits to support older drivers, and had to provide a user space that supported more than 32 bits.

The world is so much simpler if you can force al your customers to recompile their applications. If you doubt that, ask Microsoft or Intel why Itanium didn't even get a chance.

[binarycrusader]

  It also is true that (as far as I am aware) Solaris never had lots of 32-bit customers running applications and drivers that neither Sun nor those customers could recompile for 64-bits.

That is definitely not true. In fact, many of the binaries distributed with Solaris itself (even now that it has a 64-bit kernel) are still delivered as 32-bit because there's no need for them to be 64-bit (yet).

  The world is so much simpler if you can force al your customers to recompile their applications. If you doubt that, ask Microsoft or Intel why Itanium didn't even get a chance.

Except Sun/Oracle (Solaris) never required that. In fact, Solaris is famous for its backwards binary-compatibility. In fact, on Solaris 10 you can run binaries that were compiled decades ago without issue.

So I'm not sure what your point is.

[Someone]

Apple would have lost many of its top of the range customers if it had jumped directly to full 64 bit, because, due to lack of drivers (note the italics in my original post), those users would have lost the use of their expensive hardware.

Sun, AFAIK, was much more in control of its drivers, so it could move its systems to 64 bit easier.