Maybe. Though Apple gives you a lot of tools to help you make good (though simple) looking applications. UIKit is pretty detailed.
Here is my simple design advice if you don’t know how to design:
* Use the provided UI elements, they look great.
* Choose a primary color and an accent color, don’t get carried away.
* Make sure everything lines up. Choose a number (10 pts) and align everything off of that. Aligning your UI elements will go a very long ways to make everything look good.
* If you have paragraphs of text set the line height to around 1.5 (depending on the font).
* The only thing provided by Apple that is Ugly is the UIButtons. Draw a simple, clean button or ask someone to make one for you.
If you follow these simple ideas you can make a pretty good looking application without knowing how to design.
