v17.2 of the Exchange 2010 Mailbox Server Role Requirements Calculator was released yesterday with a number of bug fixes, however it's not the bug fixes that I'd like to call out, it's the virtualization support added two releases ago in case you missed it.
When designing for virtual workloads the general guidance has been to design for a physical environment, and then add 10-12% extra for the virtualization overhead. This shouldn't come as a shock, since no matter how good any virtualization vendor's marketing is, one of the drawbacks of virtualization is the performance impact due to the abstraction and emulation of physical hardware.
In other words, virtualization is never free when calculating the resources available after adding virtualization of any kind.
In Version 16.4 of the storage calculator, virtualization support was added, with particular support for planning how many cores are available to the guest machine and guidance on how to calculate the correct CPU adjustment factor for virtual processors. More on that here, follow the notes down to the version 16.4 Updates.
Personal preferences aside, the big deal for those of you who design exchange for a living is that virtualization isn't going away, it isn't free, and the tools for planning virtualized Exchange workloads just got better.