Yes and no
A number of the benefits that have been talked about only occur if the OS and app software support it; particularly graphics acceleration and low-power modes. Using very old software (or even new software missing the correct drivers) cannot take advantage of these features.
On the other hand, if you compare the same kind of software now with that of 10 years ago, the newer software requires a LOT more of the silicon to even do the same things as the old one did. Compare Office 97 and Office 2007 for example, or Windows 2k and Vista. How much more processing Word needs now, just to show letters on the screen when typed from the keyboard! Or webpages that take forever to render because the page source is the size of war and piece, with 2000 separately loaded parts and several FLASH objects.
The software companies seem to think that the improvement in silicon is not to allow a more responsive system, but to mean that clicking the menu should use 1Gflop of processing for some wacky animation, or that optimisation of their software is not required because people can just buy yet faster systems.
It is a race, and I'm not sure that the hardware is winning compared to the software.