[nness]

I've have the opposite opinion. I have found that space is a premium, even if I'm using 20gb for my VM's that's still a small portion of my Mac's SSD.

The biggest issue we had with Browserstack (and the like) was that it required us to tunnel through our proxy. Whilst I appreciate this simplifies testing localhosts, it made us all a bit nervous. Not to mention Browserstack's recent breach.

A VM is a small price to pay for an insulated and customisable testing environment. Plus some sites have the nice habit of badly crashing early IE versions, and recovery from that is quick on a VM.

Not to mention, with IE VM's we can install additional browsers (to enjoy the rendering differences in Windows and Mac Firefox versions). We can also customise IE to reflect the client's environments (for intranets or POS systems, etc). Pretty handy.