I'm a big ♥-er of this:

http://gigaom.com/2012/02/19/clearly-its-time-to-say-bye-bye-to-buttons/

Keep in mind that swiping as a button replacement only works when the UI is 100% lag free. Apple is still shipping the 3GS and not every programmer is good enough to write UI-lag free apps. As for Android, the situation is even more dismal...

Lastly, for a simple to-do list, this action is universal, but for more traditional UI's, I don't know how you would expose the functionality visually in order to convey what UI elements respond to what UI gestures.

It's a big problem right now. Apps often come with tutorials that say things like "tap and hold here to..." or "swipe here to...". If your app relies on a tutorial to expose functionality, I'd argue that you are doing it wrong.

Basically, your designers and your programmers both better be really good.

Despite all that, I agree with the general premise that it's better for everyone (users, designers, devs) that we aren't just limited to buttons anymore...