well, i just sold my rig a week ago and the plan is to order a new 2010 Mac Pro on Monday. i'm also thinking about going Windows 7 with Maya 2011. reason is because Autodesk doesn't seem to keep pace with OS X updates and the latest Apple technology as well as they do with Windows 7.
every time i talk to technical support, they don't have much to say in terms of Maya for the mac. last time i asked, technical support didn't even have Maya running on a Mac Pro. how are they suppose to help me if they don't even have a similar rig (i've noticed that many bugs are due to mac hardware and osx software issues) ? and bugs never seem to get fixed until the next Maya release. that being said, i want my new rig, if i decide to buy a Mac Pro, to be configured optimally to run Maya 2011, even though it isn't qualified to run on a new Mac Pro, or the 2009 Mac Pro, or OS X 10.6.4.
i have found with a lot of other video, audio, graphics, and visual effects software that i use, that there is an optimal amount of memory that the application can benefit from. for example, a few applications that i use see diminishing performance increases with more RAM because many applications don't use all the bandwidth available.....
what i would really like to know is what version of Maya your running and how much memory you have installed in your computer if your using a Mac Pro?