Along with the launch of Google Drive today, the company is tossing a bonus to Gmail customers as well: they'll now get 10GB of email storage at no cost. That's up from the 7.5GB that users were getting before — and as always, that number will slowly creep up over time. Google says to expect the bump as a rolling change over the next 24 hours.
If you pay for extra storage — and many users might consider doing that to take full advantage of Drive's capabilities — that storage will be shared with Gmail and you'll end up getting more than the base 10GB anyway. If you're sticking with the free product, though, bear in mind that Drive's capacity will still be limited to 5GB.