Big Iron: The 64 bit question

Which bitter flavor of OS do you currently use? BI isn't interested in XP vs Vista or Windows vs Mac vs Linux, simply:
The basic argument in favor of entering 64 bit address space is simplicity itself -- absolutely ridiculous amounts of RAM can be utilized (16 exabytes; ie, ~16.8 million TB, or ~17.2 billion GB). More memory is, in the grand scheme of things, a fine and lovely thing. To anyone who can afford an exabyte or two of quality DDR3, my contact information is in the .sig at the bottom of this article -- I have a slightly-used New York bridge and some quality Florida swampland I'd like to gauge your interest in.
The current counter-argument is two-pronged, but fundamentally variations on a single theme -- sketchy driver support and a paucity of consumer applications (and, more to the point here, games) able to take advantage of the additional memory headroom. 64 bit operating systems have only recently begun to enter the mainstream, primarily courtesy of Vista Ultimate and various flavors of Unix/Linux-based OS (including Apple's Leopard).


