I'm no Apple hater, I own an ipad and am planning on getting a macbook air soon, but for desktop computers windows is still the way to go- so much so I don't understand why you would get an imac ? If you build your own computer you can customize every single part and swap one out if you want a newer video card or get more RAM or whatever;
-Windows 8.1 pro 64-bit (Windows 8.1 is just so open, and the flaws of Windows 8 are over-emphasized, I can install anything on it, no restrictions, and having a non-crippled Office 365 2013 version is great) If you absolutely can't stand Windows there's always Hackintosh. I got 8.1 pro $70 student version
-NZXT Phantom 410 case (massive but aesthetically pleasing and good airflow) $50 with rebate, has tons of USB 3.0 and 2.0 ports, all display options you want
-Intel core i7 4790k processor (4.0 Ghz quad core) $270
-EVGA nvidia 770 Gtx GPU (Can run basically any modern game at 60 FPS 1080p) $320
-8 Gb hyperjaw RAM (Plan on upgrading to 16gb RAM when I can afford it) $70
-Seasonic 750 Watt EVO power supply (Runs beautifully quiet, can handle any editing, gaming, etc.) $100
-Samsung 250 GB SSD (Everything is blazing fast, windows startup is 3 seconds, programs open instantly) $110 on sale
-Gigabyte Z97 G1 Gaming Motherboard (Excellent overclocking options, gigabyte Bios is very intuitive, has a built in sound card and amp, good for sound quality and gaming capabilities) $140
That's $1130 for a PC that I DARE you to find an imac of equal quality/power at the same price
With the power of my Nvidia 770 GTX I also purchased an Asus 27" 1440p LED PLS display for $480, gaming is astonishingly good on this display. Maybe you could find an equivalent imac for $2,000+, but for desktops deciding on every single part, the experience of building your computer, the bang for the buck raw power, iMacs don't make sense.
I used to work at Google until a year ago. Almost 90% of their laptops were MacBook Pros/Airs and the rest being Lenovo T series and Chromebooks. On the desktop side, they had Dells, HPs, Lenovos and Macs. While the first three running Gubuntu because of reliability and security reasons, Macs were on Mac OS X. The components of those Gubuntu machines were being upgraded continuously because they were extremely underperforming and unreliable even though they usually had better specs. Most of the desktop Macs were located in Engineers' offices/cubicles. They used to save those pricy but lower spec Macs for critical tasks that needed to be performed reliably. I guess, this explains why Macs are not only the less tech oriented people's choice.
As a side note, I need to add that the majority of cellphones you see at Googleplex are iPhones. Sounds strange but true.