For the first few years of knowing about HDR I occasionally experimented with various free HDR software. Although this software varies in quality and ease of use none of it even comes close to results that come from Photomatix. None of the free software is even as good as the Light version of Photomatix. I have not tried any of the other premium HDR software but according to users on popular photography forums and file sharing sites none of it is as good as Photomatix. There is always the very occasional person who prefers software other than Photomatix but this is definitely the exception. Photomatix is always praised as superior by its users. Just do an internet search on Photomatix and you will see millions of results.
The tone-mapping function is what makes Photomatix superior. Tone mapping makes the image viewable by reducing the tonal information in an HDR image. Many programs, including Photoshop, have the ability to merge photos into an HDR image. Unfortunately an HDR image without tone-mapping is very ugly. Some people prefer the Photomatix Photoshop Plug-in. To use this program you simply use the "Merge To HDR" option in Photoshop and then use the Plug-In from the filters menu. The results are almost identical to what the standalone version of Photomatix Pro achieve.