I've been asked several times what my current setup consisted in during the last month. Since it seems something people are intrigued about I thought I'd post about it here and point people to it next time they ask :-P
I am using a MacBook Air 13" - it's the Mid-2012 model. It's upgraded quite a bit as it has 8 Gig of RAM, a 2 GHz processor and 512G SSD storage, but I still haven't bothered updating to Mavericks because I've heard stories of laptops turning into bricks, and the only bricks I want to deal with are Mozilla's.
I chose the MacBook Air over the Lenovo because everything seemed way more lightweight and streamlined, starting with the laptop itself and ending with the charger.
So far I haven't been wrong. I have been travelling quite a fair bit and I really value that I can carry the laptop with me without almost noticing (charger included). I even got an slightly smaller charger (the plug piece is slightly smaller), so considering how huge UK plugs are, that is good.
I saw some of the Lenovo laptops new hires got recently and I'm glad I didn't. The chargers are huge, the cords protruding from the chargers are thick and too long, and likewise the whole laptop feels heavier and huge. Apparently there's a "travel" charger but it seemed very large to me anyway. People run various flavours of Linux, some are having issues with things freezing randomly and webcams not quite working, whereas others are OK.
The battery in this laptop can easily last more than 6 hours while doing moderately heavy work, 8 hours when just editing text, which is quite handy when I have things to do in long-haul flights, and maybe about 3 hours when going crazy on WebGL+Web Audio. So far the only software that consistently makes the fan go crazy is Google Hangouts and its weird plug-in. And my WebAudio + WebGL + WebSockets crazy thing for JSConf.EU.
Regarding software I pretty much live between browsers, text editors, terminals, and videoconference thingies such as Vidyo or Skype, so probably there's not much of a difference between Mac or Linux here (except probably predictable webcam support). Browser wise I have all the main versions from Firefox (Nightly, Aurora, Beta and Stable), and Chrome Stable. For text editing I use MacVim with my vim profile which I install to every machine I have an account in (my profile also works with gVim in Gnome if I ever go back). I also use iTerm2 which is more palatable than the stock Terminal app. I pretty much only use node.js so most of my dependencies get managed with npm, but I use Homebrew to install the rest of stuff.
I have disabled as many stupid annoyances in Mac OS X as I could: automatic update pop ups, permission to run apps from not-the-Apple-Store pop ups, etc. Sadly although in theory you can download just a ZIP with dev tools from Apple's developer website, there were some node modules that didn't quite compile if I remember correctly, so I had to use the App Store to install the full blown XCode. It kind of irks me because it's like asking Apple for permission to develop in your machine, but huh, there's nothing I can do about it.
Ideologically speaking I certainly would prefer to use something other than Macs, but for now they are the option that worked better for my particular case. If you're moderately risk averse (i.e. don't install system updates as soon as they show up and wait a bit until they fix their bugs) they can be a pretty stable platform to work on, which is the point.
My old personal MacBook was running ArchLinux but it broke in one of the updates (something about not being able to find the partition table... sigh) and I couldn't make it work again ever after, so I have just been using the Mac partition since then.
I have reached this point where I don't quite want to spend my days fighting with config files--I just want to get stuff done, hence the stable platform requirement.