Over a year ago, I opened a case for an RFE to add Spice client support on Macs. The bugzilla is #728618. It does not seem to be going anywhere.
In the interim, I've followed this article:
It does work, but screen drawing on a Windows 7 VM is incredibly slow, to the point of being unusable. (It's fine on a RHEL VM.)
The practical consequence of this is instead of using my sleek Macbook, I have to use my clunky HP EliteBook.
Has anyone had luck getting improved performance? In the comments of the above article, someone suggested removing "Update For Windows KB2670838".