Microsoft, after repeatedly downplaying the VMware's ability to overcommit memory has...you guessed it, quietly reversed it's stance on this feature and now states "we definitely need to put that in our product". Virtualization.info is now reporting Microsoft will put this feature in an upcoming release.
However, after reading some of the comments it appears some are questioning if this feature will really perform the same "transparent page sharing" and "ballooning" advanced techniques used by VMware or is it just using swap with a GUI setting for dynamic RAM allocation. This would be similar to what you can do with VMware by assigning a large amount of RAM to a VM and then setting a limit that you can adjust dynamically (the OS will see the Full amount of RAM but vSphere only allocates to the OS the limit amount--thus causing the vm to use swap inside the VM and have Dynamic RAM adjustment.