Add quick key navigation.
When I am adding multiple memos in one sitting I'd rather keep typing and not reach for the mouse/trackpad.
Look at Remember the Milk for an example of my favorite web app. They have quick keys in their webapp that work really well.
Ps: Good job. When I saw your iPhone app a light went on in my brain and said: "This is the app you have been dreaming about: Memos with iPhone viewing+web app+web syncing+dates+date edit+TAGS!!!"
A few quick keys in the web app will go a long way! Pretty please!