It's nice to see more awareness of HDR (high dynamic range) photography. The iPhone has a built-in HDR mode, and more and more software is supporting the combining of images shot at different shutter speeds, combined to create an image that captures more shadow detail without blowing out the highlights.
HDR Darkroom Pro for OS X is on sale at a rather dramatic introductory price of US $19.99. It's a 75% off savings. Most HDR apps hover around $100 so this app qualifies as a good bargain while it is on sale.
To use the app, you import 3 or more images show at different exposure settings. HDR Pro Darkroom will align the images, and produce a tone-mapped image that will almost always be more pleasing to the eye than a single image with standard exposure. Of course, like anything, HDR can be overdone, and I've seen some pretty horrible examples of photos that were over-saturated and surreal. On the other hand, that may be the effect you are after.
HDR Pro Darkroom allows multiple methods of tone mapping, and then gives you control over white/black points, noise reduction, color balance and more. The app is very fast, easily 2-3 times as fast as my reference app, Photomatix, although it should be noted that the preview displays are very fast, the app is slow to save because that is the stage at which it renders the image. Most apps render for the preview, then do a quick save.
It's not all roses however. After processing several images, I never saw output as clean as I was getting with Photomatix, or even the built in HDR feature on Photoshop CS5. I especially saw some very rough gradients (check the gallery) when the sky faded from blue to a a bright white on a sunrise shot. Photomatix rendered the transition perfectly.
On less challenging material, HDR Darkroom Pro did quite well, but the interface is not intuitive and when you go to the help menu you are taken to the developers site and you have to hunt around for a PDF manual.
If you can work around the limitations of HDR Darkroom Pro and want to get your feet wet in HDR photography I think this app is worth a purchase at the sale price. On the other hand, it has a lot of rough edges that simply don't exist in apps like Photomatix or HDR Efex Pro. Note: There are a bewildering number of photo apps at various prices from developer Everimaging. Be sure to go the the Mac App Store on your OS X computer to get the sale price of $19.99.