I've had to run a Windows VM on a Mac because I needed to run SSMS, but if I were doing .NET development in Visual Studio and heavily using PowerShell on the command-line, I'd probably prefer to just have a Windows computer rather than having so much of my workflow inside a VM.

Because I currently work mostly on the command-line, having a rich command-line environment with access to a powerful shell and great tools is really important to me, and I wouldn't want that to be restricted to a VM.

I always thought I'd feel similarly, but I've been doing a bunch of .NET/Mono stuff in Windows 8 (instead of using Xamarin Studio), as a virtual machine in my Mac. Works pretty great, as long as I correctly train my fingers to hit the right shortcuts when in and out of the VM.

The only downside I've experienced is really one that I'll lay solely at the feet of Windows 8: If I go a long time without checking in on the Windows 8 VM, it will sometimes auto-install updates and then force a restart. This has rather horrifying results if I had also neglected to save a file I was working on.

Moving back and forth between working on the same codebase on both the Mac and Windows sides is also a little irritating; I find the best way to do this is pumping the data back and forth between them using Git. But that would be what I have to do if they were separate physical machines, too, so I'm not terribly prepared to whine about it.