Good points:
Not Windows 8.
Less expensive than Windows laptops.
Less complicated than Windows.
Should be more reliable than Windows.
Automatic updates.
Interchangeable (zero setup if you switch to a different Chromebook, just log in).
Proper keyboard (although small screen implies small keyboard).
Larger screens than on tablets.
Bad points:
Only available with relatively small screens at the moment (this is likely to improve in the future as manfacturers switch production from Windows laptops to Chromebooks).
Can't run Skype.
Printing is fiddly, you can't just plug in a printer.
Reduced functionality when there is no internet connection (this has improved; you can now continue to edit current documents etc).
Ongoing subscription cost for Google Drive after the initial period.
Can't install Windows EXE programs.
I'm not sure whether Adobe Flash Player can be used or not.
Not suitable for anyone who is paranoid about Google