Chances are, if you're using a big and soft softbox with some kind of sheet diffuser, you've found yourself with a rather boring product photograph (that is, even lighting with no contrast). Fortunately, Photoshop is here to help us achieve the kind of shot you wish. Here's a technique to add coolness to your image (it's easy, I promise).
The first step is to actually open your file in the software. Once that's all clear, I like to retouch the details first (take care of dust or other particles like it, straighten lines, get the perspective on point, etc...). Clean that image up. Then, the real technique starts.
As a starter, create a new Brightness/Contrast adjustment layer and turn the contrast up and the brightness down a bit (you could also go the other way, it's really dependant on the image). You will see your photo darken and get more constrasty.
The following step is to take the Gradient tool and, while making sure that the layer mask on the adjustment you just made is selected, and add a linear black-to-white gradient on that mask. You can go in any direction, it, again, depends on the subject of your photo. Just remember that white allows 100% of the adjustment to go through, black, 0%, and middle grey, 50%. In this case, the white section allows a darkening of the image. With the gradient on, you now have a product photo whose exposure varies smoothly from dark to the regular exposure. The longer you make the line while setting up the gradient, the smoother the result will be.
Now, if you have the product cutout from the background, you can create a clipping mask so that the adjustment will only affect the actual subject and not the background or anything else.
So, there you have it. A nice way to add interest and pop to your shot by making use of a simple little technique in Photoshop. Here's an image of an Apple TV I made a few days back.