* Well documented SDK.
* Highly secure, since all apps run sandboxed.
* Applications are highly stable.
* Abundance of resources and tutorials are available on the internet.
* Lets you access iOS core services, core services being networking and threading.
* Integrated support OpenGL ES 2.0 (OpenGL framework is used in games on iphone, ipad and ipod touch).
* Media support, iOS offers great flexibility for performing operations on audio, video and picture.
* Multi-touch support. Lots of in built touch gesture recognizers, which a programmer can use to make an app quite impressive.
* Xcode provides instruments that give you a better insight of your code, especially about memory management, if you are using MRC(Manual Refrence Counting).
* ARC (Automatic Reference Counting), introduced in iOS 5, is a great feature for programmers who are sloppy with memory management concepts.
* Usage of other languages like c. iOS uses objective c basically, but you can also use your existing c code within your iOS prgram with no extra effort. The compiler changes that c code into objective c code while compiling.
* GPU is available so that applications not built with OpenGL can still make the app rendering process faster.
* Single application for all the 3 device types, by making a universal application (iPhone, iPod touch and iPad).
* iOS SDK is also open source licensed under MIT.
Room for Improvement:
* A Mac is required for developing. Development is strictly restricted to Mac.
* Flash or shockwave videos do not run on this platform.
* ARC is not helpful in scenarios where you need control over the memory.
* Restricted to Apple devices.
* Subscription to developer program is yearly.
The SDK itself is very reliable. The documentation is also above par. The number of operations that are provided within the SDK remove the need to use any 3rd party framework for having additional functionality. I have been working on iOS and Android for more than a year now and I personally found iOS SDK to have more to offer than the Android SDK. Plus, Xcode in of itself is an excellent IDE.