Any disadvantages to Virtual Box?
No regrets except a slight performance hit on the guest machine (more RAM helps). Oh, and I felt sad when Microsoft's market cap dropped a bit in the last quarter, because there weren't as many computers sold.
And John, why do you find it advantageous to run two versions of AC at one time?
I can have my MA be logged into her account on the host and mine on the guest VM, so that she can eRx and print prescriptions. Just like the old days "Susan, call in this prescription for Mr. Smith".