Just read Aeons & Augauries' post on Spell components, and he raises a good point. Spell components seem like a very cool mechanic, until you are into actual play, and then they become just another inventory management system the Magic user's have to manage.
What is interesting is that Vancian magic is a form of imposed scarcity, where the MU is limited to a certain number of spells per day. That way keeping the Magic user from becoming a fireball turret. Spell components are a different scarcity mechanic, in that there is a limit to carrying capacity or wealth when it comes to getting these rare ingredients.
Imposing both systems on a magic user is pretty painful, so most players seem to ignore the component rules. In 4th edition, they split into two types of magic- spells that are cast and are still pretty vancian (at least the daily powers) and then ritual magic that happens outside of combat, frequently takes days to complete, and is where the really big magic is used. For the latter, the spell components are partially a 'magic tax' on the magic user, but also offers the DM adventure hooks, if he wants to make the quest for a particular rare component a requirement to complete the ritual.
Other games approached this whole problem using spell/mana points (a more abstract form of scarcity) or Sanity loss/Darkside points (basically turning it into a gambling system, where the magic user had to gauge how far they could push their luck.)
But I do think there is something interesting in using strict spell component system, where a magic user could cast as many spells as they have the correct components. The magic user could spend money/time to gather what they will need ahead of time, but they also might be able to scavenge what they need while in the dungeon. (enemy Magic users would also need to carry many of the same components.) Thus there would be more challenge to the player to think of ways of getting what their character needed. Especially if the component is defined more generally for lower level spells, and the more powerful the spell, the more specific the requirement. (like a spell that may call for dragons blood to work at 100%, can still work at 40% power with human blood, and at 5% power if you just have something red, like wine.)
It would be on the DM to keep them in check, else you might have a Magic User with a mule carrying sacks of Fireball components into the dungeon, but mules can run off at the most in opportune moments...