The benefits of using Photomatix Pro include:

Saving on lighting equipment:
Given that most digital cameras can auto-bracket at different exposures, you do not need to acquire expensive lighting equipment -and carry it- when shooting high contrast scenes. Just enable Auto Exposure Bracketing, and let Photomatix merge your photos into an image with extended dynamic range.

Saving time in post-processing:
Photomatix Pro is designed for productivity -- automatic blending, unlimited stacking, easy comparison of results and batch processing save hours of masking and layers work in image editing programs.
Taking advantage of your 32-bit images:
Have you created a 32-bit HDR image in Photoshop CS2 and could not get a good HDR conversion? The Photomatix Tone Mapping tool may help. See how it compares to Photoshop CS2 HDR conversion.

Great pictures on cloudy days:
Shadowless hazy sunlight or an overcast sky usually results in dull-looking photographs. The tone mapping tool of Photomatix Pro can turn them into great-looking images. Check this image as example.

Noise reduction:
The Exposure Blending functions of Photomatix Pro merge any number of bracketed photos -- this process is equivalent to image stacking, which tends to reduce noise in the resulting image.

Well exposed panoramas:
A panoramic scene is almost always a high contrast scene -- you can't limit your view to areas with the same brightness when shooting a 360° panorama. By taking views under several exposures and processing them in Photomatix Pro, you can create a panorama that will show details in both the dark and bright areas of the scene.