Gmail/Google Now
Last week Google announced the Gmail API as alternative to IMAP. This could mean much more intuitive integration of Gmail within other services such as composing e-mails from someone's Gmail from a web service without having going directly to their Gmail site. It's probably not something the average user will care about, but it will definitely increase Gmail accessibility. And just maybe, Apple Mail will handle Gmail correct... Maybe.
Today, I did something I've been telling myself to do for a few months. I moved my Amazon account from my Yahoo! Mail to Gmail. It probably has a larger effect than you would think. The first thing is the consolidation of emails to solely my Gmail; one source to check on all my devices. To be honest, I never had the Yahoo! Mail app on my phone. I would go to my Yahoo! Mail to check the status of one of my Amazon order; this was majority of the usage of the account. Sometimes I think I postponed my Amazon account because it was a guilty pleasure of just wasting time and slowing life down by going to my Yahoo! Mail. I wonder how often people do things because it does waste time and tends to slow life down.

So, instead of consuming time venturing off to Yahoo! Mail, all my Amazon emails will go to my Gmail. The advantage of having Google handle Amazon emails is tremendous. Just look above, it provides a link directly from the list view to the site of the order. But the best part is that Google Now will display tracking updates of packages. So this even reduces time from checking my Gmail. Just think of the time saved!
Google Now is becoming more and more useful. Of course, this involves letting Google have access to my search, location, and other personal information. But the benefits are splendid! Just the other day traveling to RI, Google Now told me when I should from my current location to get to the airport on-time!

Google is providing features in Gmail that isn't being done elsewhere to attract users to only use their service. With their expansive platform, they can develop features that can't be done by companies like Apple, Amazon, or Microsoft. Well, Microsoft could possibly do something similar but they don't have as much influence or usage at this point.