I find that Decompose scores over Photoshop by having a brush to define the transitional edge ares where pixels may be foreground image or background.
A cut-out in PhotoShop relies on performing a very accurate selection, knocking out the background and then doing a lot of smoothing of the edges. In Decompose you make a broad-brush selection of the edge area, covering the whole border between foreground and background, from which the app. calculates which is which, removes the background to transparency and gives a smooth edge.
It seems to work well even if there isn't a lot of contrast between foreground and background. If you can see it, you can cut it out.
Well worth the money to save time and effort -- and if you need to make good quality, foolproof cut-outs in a hurry, you'll thank the developers.
I think some sensitivity controls would help, and I felt the need of grab tool with a spacebar shortcut to navigate around the image, but this is only a v1.n application and these are only minor refinements that are bound to come in future releases..