Mac OS X 'Mountain Lion' has gone “golden master”, meaning its release is only a few weeks away.
MOXML won’t run on some older Macs such as the original Mac Pro 1,1. Which is just fine. Stick with what is working and ignore MOXML.
For professionals using a Mac for production work, think of your machine as a toaster— it gets your jobs done. Don’t touch MOXML with a 10 foot pole until at least 3 months of public use, where the issues can be sorted and solutions emerge. In fact, unless you’re upgrading to a new machine, you might want to not touch it at all— ever. If the toaster makes tasty lightly browned toast, leave it the heck alone!
If MOXML follows in the vein of Mac OS X Snow Lion, it will be lardered with “upgrades” that impair usability for people with real work to get done. Headaches with nothing included to compensate. Don’t rule out another eye-candy release. Wait and see if there are actually any real benefits, rather than a dilettante release oriented to those with time on their hands— Apple OS versions are no longer targeted for professionals.