Soft Shell is a bit of a confusing area as everyone seems to have differing ideas as to what it is. How we think of it is this:
Soft - ie Doesn't rely on a stiff, noisy face fabric and or membrane to keep out the elements like traditional waterproof jackets. Instead it uses a tightly woven soft face fabric often with a velour lining of some sort.
Shell - Provides good levels of water and wind resistance and a degree of warmth in one garment.
The result is to produce clothing that reduces the need for the user to carry a traditional layering system of base, mid and shell layers, although you will probably want a base layer with most of the jackets. This works because the garment will have much higher levels of breathability than traditional waterproof shells, while still keeping out all but the worst of the elements. This means that you should be able to keep yourself comfortable by venting rather than changing from one to two to three layers to keep warm and then redry. As a concept, Soft Shell has almost entirely replaced windproof fleeces, because it is more breathable and tougher.
The levels of wind and water resistance should be fine for most single day ventures where a bit of a soaking at some point in the day ins't going to be a serious issue, or where the chances of rain are lower. Soft Shell is therefore less relevant as a single garment on multi day ventures where you could get thoroughly soaked and then have to carry on in the same vein the next day. In such cases you would be better off with a classic shell and layering system for longer term comfort and safety. This doesn't mean that you still couldn't use your soft shell as part of such a system, although there are a number of better products for this use as Soft Shell tends to be heavy and is much less adaptable. For more information on the various pros and cons of softshell jackets vs waterproofs click here.
Most Soft Shell has good levels of abrasion resistance and durability. It is particularly suited to climbing as it tends to have a good degree of omni-directional stretch for ease of unrestricted movement. We also particularly like Soft Shell trousers for winter walking and climbing, and summer Alpine routes on colder faces where you need warmth, wind, water and snow-resistance but don't want to carry waterproof trousers on your lightweight dash.