Does Windows vs Linux really matter any more ?
Some people might argue that it never mattered, but I think I had a moment of insight the other evening :).
With freely available virtualisation technology it's going to matter less and less what operating system you're running or which operating system your applications need to run on.
My understanding is that Windows 7 includes "seemless" virtualisation to allow Windows XP applications to run successfully without compatibilty problems.
When Linux is able to use something like VirtualBox to provide similar seemless virtualisation functionality then it really won't matter in most cases whether your applications have been developed for Windows or Linux.
I'm currently using VirtualBox to do ASP.NET development on an XP guest using Ubuntu 9.10 as the host. XP runs "snappily" on the VirtualBox virtual machine and using Visual Studio / Photoshop is sufficiently like running it natively that it doesn't matter.
The VirtualBox virtual machine seems to have a very small memory overhead (35Mb last time I checked).
Update: It appears that VirtualBox does provide "seamless" virtualisation. This effect isn't perfect since even though the Windows XP desktop disappears, the Windows applications are not added to the Linux task bar. It works pretty well, but it's not (yet) truly seamless.