The production skills have almost no gameplay value. They can produce useful in-game things, and it is something to do as MMO players always need, but there is no fun in it. Recipe + ingredients + click + wait. It is convenient and dull, especially in volume. It encourages alt-tabbing, never a good sign for game design.
I find the gathering skills inappropriately engaging. The world is full of little boxes of candy, just for me! I was tempted to drop Blacksmithing, pick up Skinning or Herbalism, and gather my little heart out. At least you are out there doing something besides watching the little bar fill, and it progresses naturally as you play.
Blacksmithing fell down dramatically when I signed up to be an Armorer. That sends you on a quest chain calling for more than 20 stacks of metal. And I did it, since I got about half way there playing normally. I was also past level 70 by the time I went back to do it, meaning that there was no chance of having any useful crafted gear for most of my playtime, not that there would have been much of value considering quest rewards and the occasional instance visit. I gathered Thorium at the auction house so I could get the stacks of Burning Crusade metal out of my vault, and I did complete that entire tier of Blacksmithing with vaulted materials.
In terms of in-game utility, the skills look to be of interest very early and very late. This seems to be the case in most games: in the beginning, when you have nothing, crafted gear is awesome; at the end, there are a few pieces for which crafted gear is better than anything else available. In between, you spend a lot of time at the point where a few things you can make would be upgrades for a few hours. As with everything, I am told that the WotLK skills are better: they create things that everyone uses. I might have been happier had I not ended up leveling the character that took Blacksmithing; at least Engineering has mechanical squirrels.
Warcraft is not much worse at crafting than its competitors that I have tried, but it is a bad sign when a game makes me, insane trade skill addict, seriously think about chucking it and just selling all my crafting materials. That way, I could make money off all the insane trade skill addicts and have lots of vault space. (As a crafter myself, I always encourage this approach, because it increases the supply of materials while lowering my competition.) This could be a bold new catalyst for me, encouraging me to take that approach across more games. I just need for the games to stop forcing me to choose one type of node to track at a time.