Actually, I remember my finite element analysis professor running on a MBP in a VM both Catia and ANSYS, which are hungry programs resource wise. And on top of that, he was running a bunch of browser tabs, PyCharms, and a few other things on OS X. And it was impressively responsive.

I'm not saying Lightroom will run in a VM, I haven't used VMs for heavy programs, this was just an anecdote of me being surprised by how someone could use huge engineering programs inside a VM.

Lightroom is very demanding both in processing and in GPU. Also you need proper screen color calibration to get accurate results.

Personally whenever I use the clone/heal brush Lightroom slows down to almost unusable performance and this is on an i7 + 8GB RAM - I can't imagine running it in a VM. I am sure this is Adobe's fault though cause the same tools in Photoshop perform multiple times faster.

Its not about the processing but the graphics. I have tried Lightroom and Photoshop in a VM a while ago and the rendering was a little off and very slow.

The combination of GPU and what software you're using for VMs might matter too. Intel graphics are probably out. GPU virtualization is far from perfect but I've seen some surprising results.

I guess s/he means running GNU/Linux on VM.

Which is what I do nowadays, my netbook is the only surviving desktop still having a native install of GNU/Linux.