Here is a run through of what I've done - if you find this useful and think it'll help others, post it as a quote on the forum.
Step 1: Save your image as a 16bit TIFF - to do this with CS3, go under Image > Mode > 16bit.
Import your 16bit TIFF into Photomatix. Select Automate and Single Batch Processing and convert the TIFF into a Radiance RGBE. This generates a new HDR file.
Open the HDR file in Photomatix under HDR > Large File Processing, and then hit preview. This shows your HDR. Select preview size to 1024 for a larger working space. Your screen should look like this:
You can compare it with your version of the HDR on the screenshot - I did this with my secondary monitor on as well - the extra workspace really helps on editing. (You can just about make out my ballroom photos on the right monitor from the weekend that I was working on before doing this mini-walk-through).
Now back to the HDR - we will stick to the Details Enhancer. Here you can play around with your settings. Once you're happy with what you see, then save as a TIFF and go back to your photoediting software.
Here is the Tone Mapped HDR I finished and saved as a TIFF in Photomatix:
You can see it brings out the detail in around the shadows on the left bank and looks more refined than your version. You don't see the halos around objects, and here, you'll see that I didn't up the saturation as high as you did, and left it quite dark (and I hope you find, with a little mood). I added a border to finish the photo for a print.
Despite the limited resources of one JPEG, it is possible to create an HDR image from it. You don't have to have a RAW or at least 3 images to merge. Results are similar, though not the optimal for HDR photography.
Let me know if the colours seem odd to you - all my monitors are colour calibrated so they may tell you a more about what you may need to alter to balance yours.