I’ve been working with Macs and with OS X for most of the past 18 months. As a result of this, most of my hardware has shifted from generic Dell and Sony machines running Linux, to Macs running OS X. I still maintain a couple of physical Ubuntu/Debian machines, but mostly virtualise now, especially as by using powerful Apple hardware I can create VMs that are significantly more powerful than their physical counterparts.
I do most of my work on either a Macbook Pro or Macbook Air, both of which were the absolute bottom-of-the-range at the time they were purchased. I generally have one of these machines with me wherever I am. I also have access to a more powerful Mac desktop, as well as several VMs covering OS X, Windows, Debian and Ubuntu.
At home I have a 2011 Mac Mini, a generic monitor, and the same keyboard and mouse I was using 5 years ago. I back everything up to a large external hard drive and a NAS device that also streams media to an ancient Mac connected to the TV in the living room. I also have several laptops set up for specific purposes, but am in the process of moving everything important onto a series of VMs hosted on the Mac Mini.
I also have a Kindle 4 (the £89 no frills model), and am really enjoying being able to read books on the train without breaking my back or zapping the battery on my phone.
Since I went truly cross-platform, I’ve simplified things a fair bit. I use Chrome (home) and Firefox (work) for browsing, and use Google’s web-based apps for pretty much everything. At work I use Microsoft Office 2011 for those things that require it, but am getting to the point where I can be fully productive with a web browser and a terminal session. This makes moving between Mac OS X and Ubuntu easy, as does having everything I’m working on in Dropbox so that as long as I’m on one of my machines I can sync my changes back home instantly.
I think if I was starting again with setting up what I needed to make me truly productive, I’d go for a maxed out Macbook Air coupled with a 27″ Thunderbolt display in every place I worked. I’d also want a Debian or Ubuntu server to deal with backups, storage, and working on Linux specific tasks. None of this is out of the question, but is hard to justify until the machines I currently use cease to be of use.