Not only can you blend 3 or more images for HDR and tone mapping in Photomatix you can blend for different exposures.
Under 'combine' you find several options. I suppose it's a bit like PSCS2's S/H tool but you have the option of 5 variants.
You can blend any number of open images automatically for an average of the exposures, I tend to steer clear of auto anything as the result is usually a compromise.
You can blend just 2 images; you can blend the open images automatically, with manual adjustment of the blending point and the radius it affects, or you can use the Intensive method were you can select from two methods and set the degree of precision. All of these are very intuative, it's a matter of experimentation.
In all of them you also have the 'align images' feature.
Using the three exposures in the top shot, the images are, auto, adjusted and intensive high precision. the last image is the 2 image blend using the darkest and lightest exposures, a 2 stop range.
I think for some subjects this feature could be of more use than the HDR, especially the adjusted method.

There are comprehensive notes on the Photomatix site click here for the main site; here for the differences between this process and HDR/tone mapping.