MacBook Pro Retina running Bootcamp with 2 external 27" monitors
If your MacBook Retina is running in 150 DPI then your external screens will run in 150 DPI as well. This is a no go.

You can run your MacBook in eg. 1920x1200 (or any other resolution). But because this is not native resolution it is grainy. Even running with perfect pixel doubling like 1440x900 is blurry (http://apple.stackexchange.com/questions/59283/why-is-a-retina-macbook-running-1440x900-grainy-under-boot-camp). Like going from none-retina to retina (just the other way).

I have been running with the retina under Boot Camp for many weeks now, and I've given up. Yesterday I ordered a MacBook Air and I'm selling my retina on eBay (Denmark). I'm pretty tech savvy... And everybody who says retina and Windows are great lies!

You can try this on your own machine before buing a retina. Just change the DPI on your current laptop and attach an external screen and try changing the resolution to a none native resolution.

If Windows are your main OS, don't buy retina! Period.