Mike990, sums it up very well. I've been using a Project II for years but just had it totally overhauled so it looks almost new. I've just bought a Shaddow III and Project I because I like them so much. The larger ones are best in use as they make the best use of the overall concept.
Projects: Outstanding blades for soldiering, adventuring, survival or just hard work. Very tough knives with very sharp edges that give good deep cuts. Not overly heavy but still with enough oomph to chop with. Too many additional plus points to list. There are very few knives that can match the overal performance/package without giving up one or another advantage.
However, they are a specialists tool, and few people realy need such an all terrain knife and even fewer will find themselves in a position where this knife's qualities makes all the difference. But then again if you do own one then they are a real pleasure: for they are the best of type.