extracted from a whitepaper I prepared for the company I work for...
Retina Display Using a Parallels VM
Working with Windows on a retina display using a VM is very similar to the experience of Boot Camp. Parallels Desktop 8/9 provides enhanced Retina display support for Windows 7 and Windows 8 Virtual Machines. Go to Virtual Machine menu ► Configure... ► Hardware ► Video to see Resolution options for your Virtual Machine.
Definitely check out these support articles:
Parallels Mac
support article on troubleshooting retina display issues with Windows.
Retina Display using Boot Camp
When you first boot up Windows in Boot Camp on a retina display, everything will be very tiny. The easiest way to fix this is to change the display resolution in Windows to something much lower. However, you may notice that text and graphics looks a little blocky and pixelated. This bothers some people more than others - it's very subjective.
The other option is to change the DPI resolution. Windows will scale up the size of screen elements by the indicated percentage, making it easier to read. 125% works great, and 150% may work okay, but you'll start to notice various elements of the UI getting a bit out of whack. 200%, which theoretically would be similar to the way OS X works with retina, unfortunately will "break" many applications, including Revit. However, keep in mind that if you use an external display, the DPI setting will be reflected on that display as well.