Nurbs aren't used as much in Organic modeling anymore. Mostly because of they're technical restrictions. You see, Nurbs have to be constructed of uniform spans (Isoparms) in the U&V directions (Horizontal, and vertical are a good way to understand it) There can not be any changes in a spans direction. Also no more than 4 edges can meet on a Nurbs surface. Making extrusion an impossibility. So to get around this you need to use several Nurbs models Stitched together (patches) This allows for more complex objects to be constructed. But of course there are obvious pros and Cons to this method. Nurbs are surfaces constructed upon math (Bezier Math) which calculates an infinitive curve (or something alike) giving a nurbs surface Infinite smoothness. Obviously Nurbs can only appear as smooth as your computer can compute the Bezier math, But anyway, While this gives your objects a truly organic look with an easy to tweak mesh, the down side is everything's in Patches, and while you try and animate your model, you may come across tearing between the patches. which you will have to use multiple constraints, and other tools to try and cover up. Which in turn makes the animation process a royal pain.

Anyway, Nurbs are still great, people just prefer the convenience of Polygons, and Sub-D modeling better. Plus with the introduction of powerful tools like ZBrush... You can't blame us.
I still use Nurbs mostly for either roughing out forms to be converted to Polys, or for Car modeling.

Anyway, I'm just repeating everything that's already been said...

All I can say is have fun! Nurbs modeling is a great thing to learn.