Any.do might be the answer. It has the cleanest, smartest interface I've encountered. The Chrome plug-in is brilliant. It clearly has a mobile-first design (let's face it, to-do lists are most valuable when you are away from your computer).
For any to-do app to work, you have to want to use it. Any.do seems to be just that. Like any startup, I hope they can find the resources to keep it going, and keep improving. The email-to-task function could be better (I have multiple email addresses to use), and the iOS integration appears to lag slightly behind Android.
The rabbit-out-of-the-hat trick would be Salesforce.com integration...since the only thing less productive than not keeping a to-do list is managing that list in SFDC (RIP do.com!).
