Good points. Though it seems like you and the other repliers are selling him based purely on downsides of Windows. A modern Linux such as Ubuntu has more or less all of the things you've mentioned, and as a biased Gentoo Linux user I'd argue in many cases Linux does it better. ( http://www.thingsfittogether.com/2011/08/start-developing-fo... ) So it seems like you're arguing "Mac is a better environment to use VNC for your Linux than Windows is." Unless you want to convince him he also should switch to Mac for development? I'm actually curious how much the GP does on his Linux box besides development. Personally I only use Windows for games and the occasional x-to-exe conversion. (Oh and Flex development at work with Adobe's Flash Builder.)
Until you want to go mobile. Linux on a laptop is still a hit-or-miss experience w.r.t fully functioning power management, wifi without workarounds, and integrated/discrete graphics cards. I know there are perfectly working laptops available out there, but it's still a hassle to track down, find reviews, verify compatibility as stated, then actually install linux since almost nothing ships preinstalled. Then you might want to run QT/GTK/Wx/Tk stuff all side by side on the same machine and that lacks cohesiveness and makes a linux desktop feel very hacked together.
You get the features of Linux with the ability to run commercial content creation apps like Flash, Photoshop and Cubase. It's very win-win for someone who does a lot of different kinds of work. And since all the shortcuts use Command, the Control key gives you free Emacs keybindings in every text field.
I was only able to give up on Mac OS X when I decided to give up on Adobe software thanks to Adobe's abysmal customer service. Now that I don't need to be able to run Photoshop, I just use Linux.
