The Pentium 4 upgrade cycle.
My office machine is a Pentium 4. My server machine is a dual processor Pentium 4. There are Pentium 4s all over the place. These things are slow, noisy, hot and use a lot of power.
I'd love to replace all of these Pentium 4 desktops with E4500s. At some point it will happen when the old systems are through with their accounting life. For now, I turned my office desktop off when I got my MacBook Pro and just use that in the office (and everywhere else).
There are rumors of a complete redesign of the MacBook and MacBook Pro models with Montevina. Might be something that you're interested in.