With HDR it's easy to loose control. Photomatix is a power tool, one I enjoy and find amazing. However, like driving a 911 Turbo on suburban streets it's important to respect environmental limits, or you risk loosing control, crashing, and making yourself look like a teenager in your fathers car. I've done it, I know.
You may consider revisiting the HRD images with a lighter, softer hand, then converting them to black & white in CS4. (Desaturation in Photomatix is severe and not appropriate for all images, especially a woodland atmosphere). The compositional, exposure integrity of your images will come through and I think you'll have a much more pleasing result - like strolling through the woods, over a beautiful bridge.
The trick with technology, I think, is to integrate it into your work seamlessly, so no one knows it's there. Otherwise technology will get all the attention, leaving the emotion of the shot in the cold. This will rob your images of lasting, essential beauty.
I think this is a huge issue, particularly now that technology is so readily available. It's very easy to make something look cool - but cool is easily supplanted by the next cool thing - like contemporary architecture, or heavy soled, stub-nose boots. Photography isn't about fashion, or, if it is, it's only about decoration, and not Art.
Becoming a great photographer may be harder than ever, simply because it's so easy to create good looking pictures right out of the box. Anyone can do it now. Being great will require something truly innovative, and everything we do, with every shot we produce, should push us in a deeply personal photographic direction. If not, well, we can expect to make good pictures like everyone else, and there's nothing wrong with that, if that what we want.
Know your HDR environment. When you find an "open road" - a derelict building, urban blight - roadside trash - high contrast machinery - push it, hard. The results will be appropriately great.