Netbook:

>> Limited set of IO options

>> No CD/DVD unless it's through a USB CD/DVD drive

>> Less USB ports

>> No firewire (IEEE 1394/b)

>> No Serial Ports

>> Video output in some form (sometimes)

>> No PCI Express expansions

>> Gigabit ethernet only

>> Efficient processors

>> Slower, and less memory

>> Integrated GPU (shares system memory, less powerful gpu)

>> Small dim displays

>> Low resolution

>> Small keyboard

>> Etc.

If you need a $400 calculator that you can check your email with, the netbook is best... or if you need an extremely mobile computer with an IO centered around networking...

Also worth mentioning, and I would have posted this above but it's been voted on, so I can't edit...

The netbook seems like it almost never needs to be changed. You can use it literally all day (if you put it to sleep when you're not using it) and plug it in @ night, it will never die on you.

The opposite is true for notebooks. You can use it all day while it's plugged in, and get anywhere from 4-8 hours out of the battery... Mine last about 4 hours maybe a little less depending on what I'm doing (or 5-6 hours if I turn the display lights down and switch to the integrated GPU).

So another upside to netbooks, they use very little power.