Phil,
The Pro HDR Camera App works great. If people are complaining that it takes blurry pic it's because they don't know how to hold their phone still while the phone is taking a series of pictures.
Now I'm not a photography expert, but the way HDR photography works is you take a series of pictures (you allow different exposure times to capture light from different areas) and "stitch" them together. So what this app does is it takes 3 pictures of what you're looking at and then it "stitches" them together. That is how you obtain light in more than one area of the photo. A quick google or Wikipedia search will explain in more detail.
Just make sure you hold the phone still because any significant movement will blur the picture. I would say it probably takes a good 3-4 seconds to take an HDR picture. (Note this app does not replace the original camera function on the phone, so you can take a quick snapshot like normal, or use the app to get a more vibrant picture).
What's cool is after it takes the series of pictures and combines them, you can adjust brightness and contrast, etc right after it takes the picture. So you can modify the pic to your liking.
Hope this helps. You also have 15 min to get a refund after you buy the app if you don't like it. $2 is nothing anyways.
Glerp