Have been taking many HDR photos using DSLR Camera in RAW format and spent a lot of time doing post processing using Adobe Light Room 3 and HDR Soft. Some of my HDR shots could be found in the following galleries: Autumn in Oslo and London. Just to show that I am taking HDR seriously :)
Only quite recently I have my iPhone 4 after using iPhone 3G for about 2 years. (See my iPhone 3G experience.) The iPhone 4 hardware is exceptionally fast and added with superb 5 MP camera function - it could deliver a fantastic HDR shot using easy to use HDR App such as Pro HDR.
What you need is just a steady hand. The Pro HDR will take the rest. The menu is very easy to use. By choosing Auto HDR - the App will automatically checking the brightness and darkest point in the frame you selected.
All you need to do is to Tap the screen and hold your camera steady. It will take 2 frames - so it is important that your hand is not moving too much. The App would do frames alignment as part of its processing.
Above screen showing the aligning process of 2 frames shot consecutively. After few seconds (using iPhone 4 - it only take less than 5 seconds) you be presented with option to change the combined shots or save the default result. Very easy.
The following are the 2 original frames and the result.
Another example below:
The 1st frame has well lit background but dark foreground. While the 2nd frame the foreground is well lit but the background is too over exposed.
The combination of both pictures (aka HDR shots) has both foreground subject and background object ideal exposure.