Ranked in these QuestionsQuestion Ranking
Pro Pushes oneself to use (and learn how to use) cloud based solutions
With this ChromeOS also eliminates the time needed to configure the local environment.
Pro Android apps
Android apps add basic offline functionality.
Pro Booting & updating
Chrome OS boots from power off in about 7 seconds. So you don't need to leave it on and consuming power when it's not in use. You NEVER download and update any apps, although the OS does update itself. Web apps live on servers, so they're always up to date and virus free.
Pro “Just a web browser”
On the other hand it’s pretty difficult to mess up “just a web browser”. You might get a few less phone calls from your elderly relatives about how they broke their fancy new email and internet machine.
Pro Full laptop form-factor
Unlike tablets, the home of most hyper user friendly operating systems, Chromebooks come on an array of devices that don’t require you to buy any flimsy keyboard attachments.
Con You might need a cloud printer
If you don’t live in the paperless world yet and you haven’t bought a new printer in the last three years you may need money up for a new cloud enabled printer.
Con “Just a web browser”
There aren’t really any applications you can get on ChromeOS. If you can do it via Chrome you can do it on a Chromebook, but not much else.