I disagree (but then again it depends on your line of work). There was a great quote from a book about the Xerox PARC labs. I don't know the exact quote but paraphrased it was something like "I was using a word processor, sending files across our network and making calculations and realized the computer could finally do things faster then me" and that was in reference to a workstation built in the 70s.

Granted we have video games and more intense applications now but I could still develop OpenGL code on my old old Powerbook if I wanted to and be very comfortable with the results and build times. Granted my build times are something like 1 minute longer which is trivial considering the size of some projects.

The only reason I see to upgrade is when graphics chipsets have changed enough to the point I need the newer functions in them. Which takes a while because you need to keep your code runnable on older machines anyway. The only reason I went from my 4 year old Powerbook to this Macbook Pro was because I broke the screen for the 3rd time.