Now about using iPhoto as an editor:

iPhoto is amazingly powerful as a basic editor. It permits you to crop, to adjust contrast and brightness, and to adjust curves and levels.

Now I'm a professional photographer and I don't use iPhoto for anything. But there is no need for Photoshop for the average point and shooter as long as they learn to use the features under the "Edit" button and then learn to use Export. And being able to create albums and run slideshows from them by dragging and dropping the images from your library onto your album is pretty simple. It's even quite neat to discover that you can open your Screensaver and Desktop Control Panel and select one of your iPhoto albums to run as your screensaver.

Now I'm not talking professional users here. Just your average person who cuts off a bit of the top of the grandma's head during the Christmas visit. iPhoto is pretty intuitive for that type of picture taker.