All notebooks have very slow, 2.5" Hard-drives, which means it boots longer, takes longer to load apps, etc. Many come with pathetic screen cards (eg. Chips & Technology) rather that a decent (but power hungry) NVidia or 3dfx. In the past they used bad chipsets, but a lot of them use the Intel BX chipset now, so at least that's better. Still, notebooks have 100 MHz FSB at best, while new desktops have 133 MHz or 200 MHz (DDR). Also, they run ACPI and other power-management software in the background that slows up everything, while also shutting down the hard disk frequently (it takes 2 - 10 seconds to spin up again).
Because of the space & cost constraints, notebooks are often sold with a small amount of RAM - upgrading to 128 Meg is considered an optional extra. Less RAM leads to more disk swapping on an already slow Hard-drive.
The mobile Intel P3 was the first to get on-die cache (like the current Coppermine P3s and Celerons), so the CPU design was actually ahead of the desktop CPUs at the time.