I own a PowerMac G5 desktop, hooked to a 20" aluminum ACD, but i really only have it as a novelty, because I had wanted one of these since they were new, long before I could ever afford one. I have never once done any real work on it. I plan to keep it as is, until my current MBP gets a little long in the tooth, then I will use its case to build a Hack... and then buy a new MBP. I don't care for the way Apple is going now, with NONE of their systems being user serviceable/upgradable, so i want at least ONE that can be)
My primary system, is a mid-2012 cMBP. I got this particular model, factory maxed out, knowing full well the Retina machines were coming. I got this because it was the last of the "user upgradable" systems for HDD space and ram. I use it 99% of the time In clamshell mode (another reason I didn't care to wait for the Retina, who cares about the built in screen, when you're in clamshell mode nearly all of the time?), and use a 27" Acer monitor, and Apple wireless keyboard and Magic mouse (which I hated at first, but got quite use to, can't imagine using another mouse now, though I do also have a Magic Trackpad also)
I like being able to grab it at and go. We live 300 miles from ALL of our family and most friends, so we tend to travel a lot. We also enjoy trips and camping (though I see our newly acquired iPads replacing the MBP in that capacity) I like being able to have all of my data with me on longer trips though. Ive had a few unfortunate events that lead to me temporarily loosing EVERYTHING, all at once, every bit of music, documents, pictures, videos, etc, from my entire life, in one day. Now, I like the portability and simplicity of a laptop being my primary system, and use an Airport TC for backups, as well as several external HDDs for redundant backups (some stored on location, some stored and rotated off location, in various other places, all in fireproof gun safes, All of my stuff is backed up x6 right now. I will never have that same feeling of loss again)
So really, for work (website admin/creator, school (yay, USC prep, and Environmental Science, I start back to college for the first time in 10 years next month, *I am 32 years old, and stopped going to college the same semester I obtained my EMT certification, and was sworn in as a Deputy Sheriff back in my home county), and for play, (forums, craigslist apple buy/resale), my MBP is perfect for me. I don't play games, I don't have a Facebook, I really haven't gotten into photo or video editing, but plan to start teaching myself when I purchase a real camera and GoPro, some time between now, and the time the Fiancée and I become pregnant for the first time. (I have no other children and neither does she)
So, that was my long-winded answer to this poll. My G5 desk top is a very nice, very large, clock and weather display to the right of my primary screen space, and hugely inefficient, and unnecessary foot warming in beautiful SoCal. lol
*Edit, the G5 case on the left, is NOT an actual G5 any longer. It is now an empty shell, that houses my power strip/surge protector from my UPS, cable modem, one of my many external drives, and most of my cable management, which is how Ive managed to keep an Ikea Jerker, with no "hiding places" relatively cable free.
*edit 2, As for the age of everything here, besides my 'purchased well used, but still operational G5 boxes, the MBP is the next oldest. I was 100% windows just weeks after loosing all of my computers/data, and saw as a good opportunity to satisfy my curiosity about OSX, which I had never used before. Ive now gone Apple, and don't see myself going back. Love the OS, (just some of the newer hardware/machines/principals thereof I don't like, thus, the future, uh, "build" of my own system)