I find that I get the most natural results using SNS. I have purchased Nik, Photomatix, Oleoneo, and CS5. I have tried the 30 day trials of a couple of others that did not make the grade.
The natural preset as it comes out of SNS is a very good starting point. My approach to processing the file is to conceptualize it into areas of interest and to work on each area separately. You have to pay particular attention to the sliders microcontrast, microdetails, and midtone contrast. There is a tendency to pump them up and say "Wow! Look at the increased sharpness and detail." But this comes back to bite you with a non-natural look. I tend to take some of these down a bit from defaults if the area is say in shadow. If the area were brighter I might bring them up a bit. You tend to see less detail and sharpness in shadow, so this is what you expect in the image. Bright areas are just the opposite. The beauty of working these areas with mask is that you can have both in the same image. Other programs I have worked in raise the details globally which is OK is some parts of the image but not others. Then you have to do a lot of work to balance things out. The same goes with saturation. Dark areas are naturally less saturated, bright areas more so.
Although I really like SNS I must warn some about its warts. Little documentation or online info on how to use it. But it is fairly intuitive and playing around goes a long way to fixing that. There is no undo! At least that I have found. Again you develop workarounds. The brush sizes are not changeable-you must enlarge the view to get the same effect. No chromatic aberration removal. You must do that in LR and then export .tif's into SNS. No LR integration means a somewhat awkward workflow if you need to export .tif's into SNS. And a few other things that I may have forgotten. But the good news is that the developer has stated that he is working on many of these things. Considering that the developer appears to be a small one man outfit in Poland it is remarkable what he has already come up with. So, considering that, it is understandable for the lack of some feature. He does come out with frequent updates that address some of these shortcomings.
The good points:
Very natural results if desired.
The masking tool is awesome!
Many controls that address a wide range of adjustment possibilities. For example, the brightness, midtone contrast and few other tools have an option to effect only the brighter ranges. For example, saturation, has the option to effect only the saturation of the brighter areas. This is just the kind of thing that is useful and parallels how we see things.
I have not noticed any halos or artifacts - yet.
The blending of the very high areas is very smooth with little banding or color shifts. I shoot into the sun frequently and other programs have resulted in banding around the sun area which shows harshly and often with weird colors introduced. For example, I have often gotten slightly greenish bands around the sun area. I have reprocessed some of these files and have gotten excellent results without this banding problem. You can checkout and example here on this forum (without the color shift, but showing smooth transitions). Look at Erik Kaffehr CS5 version of the rock image. Look at the sunspot. The look at my SNS version latter in the post.
The controls are generally pretty intuitive and easy to use. I've used others that I had a hard time figuring out what the controls did or they forced you into some convoluted workflow. Had to do things in a certain order and going back to make adjustments was a pain.
If I seem over the top in pushing this program it is because I want this guy to make money. I want him to be able to keep pushing out all this good stuff so that I can use it. Or maybe Adobe to buy him out or hire him and bring this stuff to LR and PS.
Check out my SNS-Tutorial (post above), it will give you an idea of how the program works and its results.