I've been using Photomatix Pro version 3 for a while. It's good, but a bit geeky and doesn't really help you find a good image. I've been experimenting iwth Nik Software's HDR Efex and it's a nice step forward but I'm not yet ready to commit to it. I'm just starting to test Photomatix 4 to see whether i'll move forward with it or Nik's software. Nik has a demo you can download and try out. I like it's integration with Lightroom, but on my Mac I found it a bit laggy. Probably not surprising given how much data is being manipulated,a nd less laggy than Photomatix 3.
Okay, just did a quick test with photomatix 4. Initial thought -- definitely a step up from photomatix 3; still kinda geeky. Faster than HDR Efex by Nik but not as user friendly. The program seems to turn out images more on the "grunge" side by default (not a suprise given Trey Ratliff is an advisor) but you can tone it down. I'm going to experiment more, but right now, I'm (surprisingly enough) preferring Photomatix over HDR efex. I'm a big fan of Nik's software, I didn't expect that.
Here are some quick samples:
unprocessed image:
http://www.flickr.com/photos/chuqui/5207965359/
image out of HDR Efex Pro:
http://www.flickr.com/photos/chuqui/5208563906/
image out of Photomatix 4:
http://www.flickr.com/photos/chuqui/5275434248/
now, don't consider any of these "final" (and the subject matter isn't great, but it was handy). I tried to image them to the same general feel (i.e. "my bias" vs. the program's inate bias on how it ought to be rendered). comparing them, I think I desaturated the phtomatix more.
Both are nice tools. HDR efex is more user friendly, I think the rendering tool in Photomatix is more mature, at least on initial tests, and faster.