In the end, as Bob Dylan said, "you have to serve somebody." In the real world, where work gets done, it's really a choice between OS X and Windows, you can't put a Amiga in an office and, quite frankly there are only limited situations where a Linux box would suffice.
We use photoshop, Quark, Flash, Dreamweaver, the Microsoft suite and a significant number of other programs that only work in OS X and MSWindows. The Gimp, as fine a programme as it might be, is no Photoshop and Open office is still not really ready for prime time.
So we fight the battles we can win. I managed to convince my boss to go with an Intel Xserve and 3.5 TB raid in-spite of the fact that we could have gotten the equivalent much cheaper with generic parts. I count that as a victory of sorts but it just replaces an old PPC XServe and third part RAID, so the net number of Macs in my control remains the same - 3 Xserves, one PPC Mac handing email, two Gentoo Linux boxes and an SWindows 2003 raid box...
