High dynamic range (HDR) images enable photographers to record a greater range of tonal detail than a given camera could capture in a single photo. This opens up a whole new set of lighting possibilities which one might have previously avoided—for purely technical reasons. The new "merge to HDR" feature of Photoshop CS2 allows the photographer to combine a series of bracketed exposures into a single image which encompasses the tonal detail of the entire series.
Sarcastically saying, this magic trick saves you money for an unnecessary camera upgrade so you can invest more in lenses instead of new camera bodies.