It's a little known fact that the iPhone ARM processor can sometimes be a little slow at doing FPU calculations, this is one of the reasons Fast Fourier Transforms on the iPhone are done using radix versions than traditional floating point versions. Unfortunately not everything can be done using fixed-point transforms, especially when using vanilla C libraries designed to compile for different platforms. Not a whole lot can be done when trying to tackle the slow floating point problem on a practical level, however sometimes you will find it beneficial to disable the compiler generating optimised 'thumb' assembly. Thumb runs in 16-bit operands which improves performance and memory usage when doing regular operations, but can sometimes lead to slow floating point processing due to code having to switch back and forth from the 16-bit operands to the 32-bit operands. I find it useful when I'm making an app that relies heavily on sound processing or physics engines to toggle Thumb and see if I can gain any performance benefits:
To make your app stand out from the rest, you will need to give it a unique look and feel. Apple helps you a lot here, by making it easy to animate changes to views (which can include UILabel's, UIImageView's, UIButton's and much more). Some people may try to simulate animations using a timer and adjusting the changes over time, however this uses a lot of unnecessary resources and will certainly never be as smooth or easy as Apple's UIView animation resources. For example if I wanted to apply a 180 degree rotation on a view object, I would use the following code:
[UIView beginAnimations:nil context:nil];
[UIView setAnimationDuration:0.5];
viewObject.transform = CGAffineTransformMakeRotation((M_PI/180.0)*180.0);
[UIView commitAnimations];
This would make the object spin 180 degrees during the course of 0.5 seconds. The same technique can be applied when making changes to an objects frame, this can make it zoom across the screen or shrink/grow in an animated fashion, or combine all rotation, size and position for some neat effects.
Now something else to notice is the way I have applied the rotation code. It's important to acknowledge that the CGAffineTransformMakeRotation takes inputs as radians (where Pi is equal to 180 degrees), so we will need to convert a standard degree to a radian if we want to use them as inputs.