When I started writing on this site, we established that I'm a Mac guy. I haven't used a PC as my primary computer... well, ever. But I've also spend nearly a decade using a computer with Windows installed. And right now it's got the Windows 10 Technical Preview and Windows 8.1 both running right alongside OS X Yosemite.
Since Apple switched to Intel processors in 2006, running Windows on Mac hardware has been relatively painless. (Prior to Apple's move from the PowerPC architecture to Intel, running Windows required software emulation of Intel processors... meaning it was painfully, impossibly slow.) Mac hardware can be set to boot directly into Windows, run alongside OS X in a virtual machine, or even switch back and forth between both approaches.
The first company on the scene with virtualization software for the Mac was Parallels, with its Parallels Desktop for Mac product. The first version of Parallels was pretty much a PC inside a window running on a Mac--your average virtual-machine display, in other words--but it's come a long way since then. The $80 Parallels Desktop 10.1.4, released earlier this week, supports the Windows 10 Technical Preview--and a whole lot more.
As you might expect, virtualization leader VMWare is also in the game, with the $70 VMWare Fusion 7, another excellent option for running Windows and Windows apps inside OS X. And Oracle's free open-source VirtualBox is there too, lacking the polish of the commercial apps, but at a price you just can't beat.
Parallels Desktop and VMWare Fusion excel at integrating the Windows and Mac environments into one. I was going to call it a "seamless whole," but that's not really accurate. These are two different operating systems which sometimes use very different metaphors, and so there are most definitely seams. But it's as seamless as one could hope for, and nothing short of miraculous for anyone who used Virtual PC on the Mac in the early days.
Windows apps can now run in their own windows, intermingled with Mac windows. Windows apps appear in the Mac's Dock. The clipboard and file systems can be shared, and the Start Menu can appear in the Mac's menu bar or Dock. If that's too much commingling for you, you can also set Windows to run in its own full-screen Space. In that scenario, a brief swipe on a trackpad can move you from an all-Mac environment to an all-Windows world in a fraction of a second.
As a longtime Mac user, I have to admit that I can't decide which approach I prefer. If I'm running a single Windows app, I usually prefer for it to float among my other Mac apps. But if I'm switching between many Windows apps and managing files, it feels more natural to see the entire Windows interface. I might describe it this way: If I'm using a Windows app, I want it to just feel like one of my Mac apps. If I'm using Windows, I want it to be purely Windows.
As with virtualization on Windows, these Mac virtualization apps can run more than one VM. In addition to Windows and Linux, both Parallels Desktop and VMWare Fusion support virtualized versions of OS X. OS X 10.6 and earlier can only be virtualized by using the more expensive Server variant; Apple changed its virtualization license so that the mainstream consumer version of OS X 10.7 and later can be virtualized.
Both Parallels Desktop and VMWare Fusion are widely liked--it's one of the rare examples on the Mac where two major software vendors are spending a lot of effort to compete directly with one another, and the quality and diversity of features of both apps is a happy result. Tests seem to suggest that Parallels 10 is a bit faster and smoother than Fusion. If your company is already using VMWare's products elsewhere, that might be a better option just out of convenience.
If you'd like to use Mac hardware to boot directly into Windows--no Mac layer whatsoever--that's what Apple's Boot Camp is for. Boot Camp is a free download from Apple that allows you to create a Windows partition on a Mac's hard drive and install Windows-compatible drivers for that Mac's onboard hardware. Once you walk through the process and install a copy of Windows, the Mac is essentially a dual-boot system; hold down the Option key at launch and you can pick Mac or Windows.
These two approaches actually work pretty well together. You can set up a Boot Camp partition and then point either VMWare Fusion or Parallels Desktop at it, and the virtualization software can use that partition to drive its VM. This is the setup I have on my iMac: a Boot Camp partition that's also selected in my virtualization software. It works surprisingly well, though I have to remember to shut down the virtual machine before attempting to reboot into Windows via Boot Camp, or things can get a little weird.
As for me, I'm not a heavy user of Windows. I have a few go-to programs that only run on Windows, including a baseball game that I'm particularly fond of. I appreciate being able to reboot into Windows via Boot Camp and play PC games at native speeds. There are moments in the sometimes painfully laggy development of Office for Mac when I'd prefer to use Word or Excel running on Windows to the native Mac version. (And back when Office for Mac temporarily dropped support for Visual Basic macros entirely, I was not alone!)
Back when I worked at Macworld, we did a cover story once called "I'm a PC," which alleged that one of the best PCs in the world was a Mac. Apple's hardware design is excellent, and if you're someone who wants to run both OS X and Windows, there's no other option! I have met people who loved Apple laptops so much that they would buy them, use Boot Camp to install Windows on them, and then use them primarily as Windows PCs. Those people were a little crazy--but what they were doing wasn't impossible, just a little impractical.
If you want to just use a PC, you should buy a PC. But Mac users who need to rely on PC software have spent the last eight years not having to carry around two computer, and today's virtualization software makes it seamless to switch between the two operating systems. It's a great time to live on two platforms.