I have to say the lighting on the left part of the image and especially on the fake stones looks really good!
I'm not fond of the texturing of the soil/ground, to be honest I think it should really need some work to get this image really working.
The atmo is nice also. In overall good work.
What did you do in Photomatix? I'm not familiar with it, can you do things you can't in Photoshop?
Martin