At customer events a few years ago, we started handing out one-page "Survival Guides" (printed both sides and laminated) with links to important resources. The wiki versions of the Survival Guides are meant to do the same things without killing trees or using laminating machines. This one is for a new feature available in Windows Server 2008 R2 SP1, in Beta at the time of this writing.
Completely shut down (not save state) your virtual machine and merge snapshots. Saved States are not compatible between different Hyper-V versions. NOTE: merging your snapshots may take some time.
Install Service Pack 1 on the parent partition, then click Restart.
The product group has the definitive series of blog posts on Dynamic Memory, now available in Windows Server 2008 R2 SP1 Beta
TechEd Demo: Hyper-V and Dynamic Memory in Depth