Are you talking about the Pentium 3 chip itself? And do you mean in relation to other chips of it's time or now? Has no advantages now over anything. I guess maybe the chip that runs the lights in the Barbie Pink Monster Truck is slower than a P3, but not much else is.
Look here for info http://en.wikipedia.org/wiki/Pentium_III
You may want to dig up some archived computer magazines for reviews of the chip and systems it was in also.