For the past year we have been hearing a lot more of 64-bit as the next big step in personal computing. Put in simple terms, going 64-bit would double the amount of data a CPU can process per clock cycle.
[COLOR=royalblue]It's true a 64-bit desktop computer won't make your word processing program run faster (sorry, you're the bottleneck in that equation). But a 64-bit chip has the power to dramatically improve the performance of your more demanding applications, such as audio and video encoding, complex engineering programs like CAD, and--of course--games. And in the long term, 64-bit computing will give programmers much more power to play with, and could revolutionize what desktop software can do.[/COLOR]
Intel has been offering Itaniums to the server and workstation markets for some time now, we all know AMD Opterons are available already & AMD's next mainstream piece, the Athlon 64 will arrive later this year. PC World has an article explaining short and long-term advantages
we are most likely to see with the arrival of the next generation of desktop computers.