Which program do I use the most? Easy: Emacs and Firefox. Which I could probably run--just as easily--on virtually any computer imaginable.
Emacs really speaks for itself; "eight megabytes and constantly swapping" is not an insult any more. In the grand scheme of things, Emacs uses essentially no resources.
And Firefox is good for two reasons: it's pretty efficient as is, and I don't visit many heavy websites. Hacker News, StackOverflow, Reddit, Google, hackage, Wikipedia and so on could easily be rendered by even the weakest of computers.
I am definitely sure that I could get by on a significantly weaker computer than somebody with less technical acumen. But would I? No! I love my useless desktop effects, my silly widgets and my 20-second boot. I like my programs opening in seconds. And I certainly enjoy having more computer power than I strictly need.
So while I'm pretty sure I require far less computer resources than most people, I'm still going to get a nicer computer than I strictly have to. Just because I can.
Just an amusing observation I've had about myself.
An observation that I've made after using (a later, the first one broke) netbook with a conventional build versus the same netbook with a SSD is that with a hard drive, netbooks are painfully slow. Once you've swapped that for a really fast SSD, and stopped using Windows on it, it boots in 10-15 seconds and programs usually launch almost-instantaneously. I've found it to be almost as nice to use as my (much nicer and newer, quad core with a nice graphics card) desktop. There are exceptions to the 'almost as nice': flash doesn't work well, screen size is an annoyance sometimes, and you clearly aren't going to be doing much with CUDA. But considering it cost ~$550 with the SSD (which was almost as expensive as the netbook), as compared to well over $1000 for the desktop+screens, it's pretty awesome (and portable, too) for someone who doesn't always have extra cash (students don't have the best salary).