I have been working with the VMware Fusion 4 beta software for some time, and this version is absolute perfect!
VMware Fusion4 is now official released and because it is so seamlessly integrated with the mac OSX, you sometimes forget you are working on a Mac )
This new version support x64 Virtual Machines so running vSphere5 (x64) nested works perfectly.
On top of the x64 Virtual Machines support, VMware was able to squeeze more than 90 new features in this version.
Now for a limited time VMware Fusion 4 is available for the Mac users for only $49.95 (!) you can get it online here: http://www.vmware.com/a/buylink/47
even better; if you type the promo code FUSION20 here on this portal you will see an even better price-drop