Linux or BSD is where it's at for hackers. MacOS is nice too, of course, it's simple enough that my mom can use it. Just that if you really want to be in control of things, you probably want Linux. If I had to do sales or something else where looking flashy was important, I guess that would be another place where Apple's very nice looking products would be a good pick, but Dell+Ubuntu is a much better price/performance bet for someone who just wants to hack, a lot, and enjoys the freedom and control that come with free software. Admittedly, not for everyone, but then again, this site is for hackers, right?.
I want to be in complete control in my production machines (aka servers) not in my development machines. When I want to code I want to get it with the minimum hassle.
It's not exactly tough to code on Linux, so it's not an 'either or' proposition. Furthermore, you get the added bonus that if you set things up right, you can have very similar environments on your desktop and server.
And even on your desktop, there are good reasons to have more control than Apple might allow you to have. Steve Yegge's focus follows mouse rant is a great one:
I code on Kubuntu using vim. Macs are too expensive in my area + i don't really know of any advantages to kubuntu other than the prettier interface. My kde desktop is really fast and i can do my daily tasks really fast so i have no problem with it. Macs are probably cool too, but i enjoy flexibility more than pretty icons, and my crystal clear icons are pretty enough for me.
I will never cease to be amazed by how nerds can imagine anything (and read crazy sci-fi about it), but if an object can be described as "pretty", it cannot have any other positive traits.
That wasn't my point at all, and there are plenty of things to which I would ascribe many positive attributes including pretty - first and foremost my wife, who quite smart, and also pretty.