Really? In 2003 most of us were working on G4 Macs, Pentium IVs at 3Ghz or even Xeons. Emacs worked fine and very fast on all those machines.
Personally I have been using Emacs since around 1997 and even then it was not slow. Not on intel machines that were slow by today's standard and it was certainly not slow on the Sun Sparcs that I used to work with and develop on.
I think the author is confused and really meant to say: emacs had a reputation of being slow. Considering emacs originated in 1976 this is not surprising.