Whether to virtualize or not is the question for many companies today. All components of FIM 2010 R2 can be virtualized. If you have chosen to virtualize your SQL servers, I guess every other service will be virtualized as well. A starting point for the discussion on virtualization is available at http://aka.ms/VirtualizationBestPractices.
If I have noticed one thing during my years as a consultant, it is that customers tend to give virtual machines only one virtual CPU. However, almost every FIM feature can benefit from multiple CPUs, and I would recommend giving at least two to three CPUs to your FIM servers, depending on how you co-locate different FIM features.
The FIM development server at The Company, for example, has two CPUs and 4 GB of RAM. If your test development server is to load and manage all your identities, you will likely need to add more RAM to that system.
