I have been learning Blender for the past several months, and I just discovered the Blender 3D: Noob to Pro wikibook. Although I'm not a complete novice, I have started from the beginning of the book to fill in the holes in my knowledge (since I have used various tutorials until now). If I plan on just using cycles render from now on, would I be wasting my time to go through the "Section 2C: Materials and Textures" part? I have a basic understanding of materials and textures, but as I said, there are several holes in my knowledge there. Is knowing the Blender internal renderer settings for materials and textures important for using the Cycles renderer?
Short answer: nope.
Cycles and BI work very differently, consequently materials are completely different for the two, both in the way they are defined and calculated. I think learning BI first often does more damage than good when switching to Cycles.
I should note that some people do say new users should start with BI since it is (arguably) simpler than Cycles. I heartily disagree with this view though. Cycles may be a little more complex to some people due to it's much greater flexibility, but I don't see any reason why starting with BI would help one learn Cycles.
I think the idea that BI is "simpler" is a misnomer though, it's just different. Personally, I find Cycles's nodes to be a much more intuitive way of defining materials than BI's wall of settings for everything under the sun. Which one really is simpler is a matter of opinion, so neither one comparatively blows the other out of the water and should.
I concur with the answer that PGmath gave for the most part, but I think there needs to be just a bit more nuance there, because the answer to the original question depends to a significant degree to your intended use of Blender. If you are making stand alone Blender renders and animations, cycles is the way to go.
However, if you are making content for use for export to other platforms, Cycles is probably not going to be very useful at the moment, as to my knowledge, none of the external platforms, such as external game engines, support cycles, so anything done for that will need to be in Blender Internal. Also, as far as I know, as of the writing of this answer, if you want to export a decorated object, anything that is going to be exported to a different modeling platform will not be able to make use of cycles. Of course, it is possible this might change, as it seems to me that a node, or family of nodes, could be devised so that an object in which cycles is used could be exported for platforms in which it is not.