Notational velocity on the Mac, notes.app in iOS
I use Notational Velocity and Simplenote apps on iPhone and iPad and the Simplenote web site as well and while I see you want to stick with Apple's notes.app I think you'll find Simplenote excellent, maybe better. I've been using it as long as it's been out and it's stable, simple, and has always worked for me.

If Apple mated the Notes app with something on the Mac I might never have tried Simplenote but it's cumbersome as you say to have to use Mail to deal with notes. Notational Velocity's integration with Simplenote is probably what you're looking for.

Simplenote is free, give it a go.