This is an excellent iPhone app, allowing me to test shader techniques on the go. But the best part about it is that it actually has syntax highlighting, something other code editors on iOS seem to neglect. Sure, it blurs when you type, but it is worth it for the readability for the code you type.
The only reason I give it 4 stars is that it does not have a blank template, you can only "clone" the shader projects in the app. Also, it does not have key shortcuts, like curly braces and brackets, that other code editors have.
This is a great editor, and it is well worth the $5 that I payed for for missing the launch. :)
Pikko CD about GLSL Studio