If you find that, despite the improvements addressed in System Center 2012 R2, deploying virtual machine workloads is a slow process and takes a lot of unnecessary effort, you'll want to download the latest CodePlex release of the VM Role Authoring Tool.
The VM Role Authoring Tool is used to author VM Role artifacts - Resource Definition and Resource Extension Packages.
The download is here: VM Role Authoring Tool on CodePlex
Microsoft's Charles Joy has put together some intro videos to help understand the usefulness of the new tool. Here they are:
Creating a Windows Server VM Role Resource Definition
Creating a Windows Server VM Role Resource Extension
Creating a Linux VM Role Resource Definition
Updating a Virtual Machine Role Gallery Item