I have heard from others they improve your rate of success. A few have said that they increase your skill slightly. I have no facts to back up these claims as I have not tested them personally. They are simply rumour. I would assume though on basic common sense that they have to have some affect on your crafting or else there would be no point in having them in the game.
That's what I was thinking too but when I examine them they don't really say much. I guess I'm gonna have to give it a shot seeing as how I suck now as it is. =)
the skill are a major PITA to level. They go up pretty slow (besides gathering; I always get good gains in it). As for the descriptions, I have found them to be severely lacking on most items in this game so far.