Well, the full domain will probably give you a hint of why I'd want a very solid "twist" before I went up against it: https://keep.google.com/ It's a default install on many Android phones I've had. Your app isn't going to get that.
And, just because I've been on the internet a while and I know what comes next, let me repeat my point: Yes, you can compete with built-in apps, but you need a twist. "Shared lists" is a solved problem; if that's all you've got, you've got nothing.
