Do you use VMs for developing server side? I haven't had a great experience with Virtualbox and VMWare yet, and VPSes are 150ms away, unfortunately...
Since we use programming languages with rich runtimes like Java and .NET, POSIX compatibility usually doesn't play a role.
When it does, we use VMWare with Ubuntu or Red-Hat distributions.
Since I became a 100% laptop user, my GNU/Linux usage has been constrained to VMs, server and a small netbook I use to travel. But zero Mac OS X around me.
Love the OS with its NeXTStep roots, but could never get myself to pay the 1000 euros difference to get a Mac that would be somehow comparable to e.g. Thinkpad W510 in terms of available CPU/discrete graphics.
Also for better or worse, my Windows roots go all the way to Windows 3.1/Win 16, so those skills are quite valuable in the enterprise. And I enjoy the love C++, .NET and Java have on the platform anyway.
iOS is the only thing that might force me to eventually get a Mac, but so far Android and Windows Phone already keep me busy enough.