Years and years ago, when dinosaurs roamed the earth, when a 68020 was considered blisteringly fast, and when I was about to buy my first computer (a PC-XT clone from Epson, since as a postgrad student I could not afford a Mac), I went to the library and read up on the theory and practice of buying a personal computer. This was in the days when a computer was a luxury rather than a commodity, and so in a sense before we quite knew what they were. Accordingly, there used to be books on the subject, with chapter titles like, "What is a Computer?" or "What Can You Do with a Computer?"
I had worked with text on a mainframe previously (using Scribe, which was a little like TeX), so it was not all entirely novel, but having a computer of my own did really represent a shift in how I lived and worked. I found a piece of sage advice in the book I picked up, and I think it has served me well over the years: you don't really use a computer, what you really use is software. So think first of what software you want to run, since the computer you choose should be chosen with a view to what you want/need software to do. I have kept that piece of wisdom in my head all these years.
For instance, my MacBook Pro (latest issue -- I do have to use up to date tools also) will not run a good deal of the software I have found, purchased, invested time on learning, and so on, and that I would still like to run, dammit! Much of my most useful software is PPC-based. Some things the MBP really ought to run it will run at best in patchy fashion (e.g., there are small bits and pieces of older "Universal binary" versions of FileMaker (v. 9) that will not run without Rosetta). So if I want to use some of my perfectly-good software, and avoid the most egregious assaults of the kind of "progress" that just leaves me doing the same things, at much the same pace, but much more expensively, I need tools to run it on.
Similarly, if I want to run decent open-source software, or the latest from Microsoft, I can forget about a PPC machine. So I have, for instance, a cheap AMD-based ThinkPad running Ubuntu, and a MBP with Mountain Lion. I need those for certain things. But for PPC software, you cannot beat a G5, and a high-end G5 will run PPC software with aplomb. So, as long as the PPC software meets my needs, so will a G5.
Eventually, inevitably, my PPC software will cease to be quite so useful, and then I'll have to move on, but happily, I have some way to go still before that happens. I think eventually that I will likely move to some version of Linux, as I have been experimenting with it, and like what I see (in some major ways it reminds me of what it was like to use a Mac in the mid-90s, bucking the trend and all that), but that is for another day.
For people who work in software development, of course, or who are serious about games, or who want to watch internet video 24/7, the day to switch came some time ago. Hence the loathing for the G5 from certain quarters. Me? I just need to read and produce text, exchange it with peers, record/edit/publish basic audio (human speech), run a database, and network with perfectly serviceable printers etc. from days of yore that it would be madness to throw out, or to throw out just yet. For this sort of thing, a G5 suits me to a T, better than the newer stuff in fact.
Having a quad to play with now is icing on the cake.
