I use Gmail as the backbone of everything digital that I do. I use the app as well as the email service. If an important attachment comes in an email that I might need in a meeting, I store it in Google Drive because I only carry a phone and almost never a laptop or tablet. If I carried a laptop I would store attachments in Dropbox, which has been my principal storage/backup since the day Dropbox came out of Beta. Anything really important is stored in Dropbox. It is much easier to store a Gmail attachment in Google Drive than Dropbox, although it can be done. I take all my notes in Evernote, which is probably the best product I use.
I have been a particularly confirmed user of Dropbox and Evernote since the day Google cancelled Google Reader, their RSS reader. I read about 200 blogs more or less ever day and moving that "library" after Google Reader died was important to me and not trivial. From that day on I have no archive of my information with Google, Apple, Microsoft or another mega-app provider.[I don't consider the Gmail archive of emails to be very important.] I prefer my critical apps to be from single app companies, companies where the sole purpose of the company is a single app.
This strategy may now be in question. Google and Evernote have announced an agreement whereby Evernote can access Google Drive files. Is Google the camel putting its nose under the tent of Evernote. Is Evernote independence now in question? Will Microsoft swallow Dropbox next? As sad as it would be to lose Evernote to Google, it would be a tragedy for Dropbox to lose its independence. In my mind Dropbox is the app that made the mobile device era when it permitted the most simple way to synch documents across multiple devices.