iPhoto Batch Enhancer is a nice addition to iPhoto. It comes in handy when you want to process several photos at once using iPhoto. The application doesn't really do anything but tell iPhoto how you want to enhance the pictures. The good thing about is that, apart from letting you process several pics at once, you can also enhance the pics in different ways. In other words, you can "chain" the modifications.
The first thing you have to do is make a selection in iPhoto of the images that you want to process. Once you have done that, you can go to iPhoto Batch Enhancer and start choosing the way in which you want to enhance your images. The main window shows a small drop-down menu with all the available actions. To its left are three buttons, which work like categories for these actions. For example, the first button shows actions like enhance, black and white, sepia, antique, fade color, etc. The second one lets you add contrast, invert, tint blue, etc. By clicking the "+" button at the right, you add another row, which lets you add a different effect to the same pictures. You can add as many as you want.
iPhoto Batch Enhancer saves you a lot of time if you want to add multiple effects to several pictures. In my testing, it worked very well.