I polled a room of data professionals this week while speaking at a paid event, 56 people. All of them are using virtualization in one capacity or another. So yes, it is good to put SQL Servers in a virtual environment. Further, a lot people are now paying for virtualization through cloud services, either AWS or Azure.
Yes, it's not just safe, but a good idea to use virtualization with SQL Server.
Now, advice on what you need to measure? I don't know what your desire is for moving to virtualization. Are you trying to consolidate hardware so you use less? Are you trying to take advantage of virtualization's abilities to build servers quickly on the fly? There's just so much to talk about here that it's really hard to narrow down to a set of advice.
What is your goal for virtualization?