I am so excited! I just got my newest portrait lens today. It's a Tamron SP 70-200mm f/2.8 Di VC USD. This is the perfect complement to my Tamron 24-70 f/2.8 Di VC USD. Together, these (and their OEM counterparts) are considered the top of the line for portrait lenses. I did a lot of research before this purchase, primarily because of the expense.
Once again, I found Tony Northrup's videos to be immensely helpful, especially this one: https://www.youtube.com/watch?v=P80BpSQIIto I can't wait to capture some beautiful images with this awesome lens!