Using the app is simple. First, type what you want Obama or Bush to say, then you'll receive a link to a .m4r file via email. Install it as you would any other ringtone. You can also get an mp3 file for non-Apple devices. The Obama and Bush voices sound reasonably close to the real people, and, of course, you can have them say anything you want, funny or serious.
The onscreen directions are pretty straightforward. Type the text you want spoken, add some sound effects if you like, like the Hail to the Chief music, and send it out for processing. To do that you hit a button marked 'action' but it wasn't clear if it worked because there is no feedback that the data has been sent. It seems an easy fix for the developers.
The app allows you to create 10 different ringtones, after that you have to pay via in-app purchase for more. $0.99 gets you ten more, and $4.99 lets you create 50. I would think the average person can get along fine with 10.
Ringtone Director Presidential Edition is a cute novelty. It's a little trouble to go back to iTunes to install the ringtones, but that's Apple policy.
Ringtone Director requires iOS 4.3 or later, and is optimized for the iPhone 5 series. It's a universal app, but is obviously more suited to the iPhone.