Compare Evernote with Google Keep. The latter, which came out later, converted me to use the former. You have nothing to worry about. A big company sucks at copying ideas. An innovative big company gives incentives to defensive maneuvers like this, but never sees them through to an offensive maneuver unless there's billions at immediate risk. If anything, Google is doing you a favor by shining the spotlight on a mediocre solution. All you need now is the product to tap into that dissatisfied channel. They just validated the significance of your market for you. Good luck!