When you hit that A-ha moment in Portal, you can finish a computer game.

When you hit that A-ha moment in Photoshop (this might take a few years) you can literally make a career out of it.

I don't think Photoshop is hard to use but that's because I've been using it for 10 years.

Mocking the complexity of iPhoto on the iPad is unfair because it's the first application trying to do something advanced on a touch platform with limited capabilities, no keyboard input, no mouse. They are exploring new ground which should be applauded.

The people who had their A-ha moment with iPhoto for iPad now have a powerful tool. An application like Snapseed for iPad may be easier to use but it also doesn't have as much features. If you only have 1 feature, an app is going to be simple (think the first iDVD).

What is the best way to make an interface learnable? A certain crowd will want documentation, books and videos. Another crowd wants to be guided within the application.

I think most of it depends on whether you're going to do something 100 times or once. If I'm playing a game I want to be guided by the game. If I'm cropping a photo in Photoshop I want to be able to hit "C" for the cropping tool because I'm going to do that a gazillion times in my life.