Rgillard:
In a previous life I ran an engineering department where we used Solidworks in conjunction with our CNC machines. Our group developed systems for scientific research, so we were able to dream up some really neat stuff. Lots of fun. Solidworks will also do mechanisms with animation.
PineRidge:
Obviously how long it takes to get comfortable with something is dependent as much on the person as what the something is. However, having dealt with a lot of software of an engineering nature I would say that Solidworks and other similar parametric modeling systems are really easy to get value out of quickly. I was able to make basic objects and assemblies literally within minutes of my first encounter with the package. My experience with Autocad, for example, was not the same.