The most I've paid for an iPhone app is $5.99. This is why I was so excited to get a a promotional code for the $19.99 Human Atlas and install the software on my iPhone 3G right away. The app also works on the iPod Touch.
Human Atlas offers 3D images and videos of 150 common medical treatments and conditions. After a few days of use, I think this is a great application for those who want to learn about their body and conditions ranging from allergies, muscle pain, high blood pressure, stroke, and tendon injuries to diabetes, cancer, HIV/AIDS, and more.
Basically, you will appreciate anything you can learn from this app.
What you won't appreciate, however, is its lacks of features. The Human Atlas app has two parts: 3D image and video. The images don't allow for rotating the body, you're stuck with the front of the object. This makes the images seems less "3D" than they could be. Also, you can't display the images vertically. While it's OK to watch the video with the phone put in the horizontal position, the images could benefit a lot more from the vertical display as you won't have to scroll as much.
The biggest shortcoming of the app, however, is the fact that it requires an active Internet connection to work. The app won't even launch if you're not connected. This means you will not be able to use it as a time killer, say, on an airplane.
Also, as videos seem to be hosted somewhere else, you'd better use a Wi-Fi connection if you want to view them. I tried to play video via 3G and Edge connections and that required a lot of patience. There's no way you can save them to view later offline, either. The app's video section's performance is much like that of YouTube on your iPhone.
So all in all, this is a very informative, educational, and fun app to use. However, it does have a lot of room for improvement. Personally, I'd love to see it be able to work offline, at least the image part.
But that's just a suggestion, not a complaint. After all, I got the app for free.