OpenSolaris doesn’t like 512MiB of memory
The problem is, unlike FreeBSD and most GNU/Linux distributions OpenSolaris doesn't allow text based installations (to the best of my knowledge), which means you have to boot off the CD and load an entire live Gnome graphical environment into memory. I think this is a serious flaw and doesn't help to sway the rallying point that Jonathan Schwartz made in the early 2000s when he called it Slowlaris! But that's for another post when I have more information.
Because I only have 512MiB of memory in this machine it means the optical drive is constantly thrashing to unload and reload that last 200MiB+ of data that doesn't fit. The result is the installer took over 1.5 hours just to reach the screen where I could enter the timezone information of all things. I gave up at this point, perhaps if I had persevered for another 3 or 4 hours I may have got it installed.
As I said in my earlier post this machine supports up to 1.5GiB of memory so I intend to grab a Kingston 1GiB memory module (#KVR333X72C25-1G) as soon as I can afford AU$80, in which case I might be able to give OpenSolaris another try. For now it's back to my beloved FreeBSD or to Debian.