Google Now is a service that you can either like or not use - it's really hard to hate it. I was always a big fan of Google Now on Android and now the same notifications (well, maybe not exactly), are available on Ubuntu desktop too.
|Google Now notification in Ubuntu.|
Google Chrome (unstable) offers new Notification Center but also Aura UI and App Launcher that allows you to easily find and start Chrome Apps.
If you already installed unstable edition of Chrome, all you need to do is update it to latest version:
sudo apt-get update
sudo apt-get install google-chrome-unstable
For people using stable edition, Google releases packages (dev-edition) with newest releases. Unfortunately if you want to test unstable Chrome, you have to remove stable edition.
A lot to do
Unfortunately right now notification in Chrome are far from perfect. Biggest issue right now is the fact that they sometimes doesn't work at all - but of course it's still unstable release so it should be used for test purposes only.