Just thought of one potential hitch...
If one is running a browser in a sandbox, can the browsing protection feature of the system's anti-virus software still monitor it? Or are the two completely isolated from each other? If the latter , then sandboxing a browser would be slightly self defeating in this regard.
In theory, I believe you could install a virus scanner inside the Sandbox...
...though I don't know why you would. EVERYHTING you do, unless backed up before closing, becomes lost forever and does not transfer to your OS proper.
As for me, I'm back to using Linux Mint for my internet needs and my Windows machine stays offline and dedicated soley to Audio/Video Editing, Video Game Design, and Gaming.
Keeps life simple, though for course dedicated machines isn't for everyone.