To say I'm all in when it comes to Google is an understatement. Some people are all in for the Microsoft ecosystem, others for the Facebook ecosystem, but I drank the Goolge KoolAid in every way and have not regretted it at all. (No, Apple doesn't have a similar ecosystem. Not in the way that Google, Microsoft, Yahoo!, or Facebook do.)
Part of the advantage to being all in on Google is that your information isn't siloed into a single product. For example, Gmail can access your Calendar. Your Calendar can access your Hangouts. Documents in Drive can be embedded in Sites. This sort of sharability is what made Microsoft Office so powerful on the desktop. It is what has made Google Apps even more powerful on the internet.
The biggest benefit for me has been Google Now. I store my browsing history in my Google account. I store my Calendar in my Google account. My email is in my Gmail. I keep my location history in my Google Account. All these kinds of things combine to create a really powerful and useful tool that can tell me what is happening based on my preferences. It can let me know ahead of time if traffic is going to be bad. It can tell me about news and events it thinks I might be interested in. Facebook do similar with their Newsfeed as well, but it's only on their site or in their apps that it's useful. Google Now transcends that with Now on Tap.
Now on Tap is a contextual, and app aware, application that can use the information on your screen to provide you even more useful functionality. Search further for something someone says in Hangouts or mentions on Twitter. Add calendar events easily. Hear a song on Spotify? Want to know more about it? Now on Tap can give you that information.
It does take some practice initially. Most people have never had access to this kind of functionality. But the more you use it, the more you realise you don't want to be without it ;-)