I can't believe all these responses, specifically this one, from page one: "No matter what George Lucas does to damage the franchise, there are skilled writers who can fix it down the line." Did he not create this entire alternate universe? I understand the point you're trying to make, but it seems contradictory to say that one of the most successful film franchises of all-time is "damaged" by it's own creator, and then repaired by those following in the wake of his success.
As for all these people that say "it takes the magic out of it," keep in mind that the description given to Schmi (Anakin's mother, SP?) by Qui-Gon, which I assume is the topic of this debate, is a vague description given to an "ignorant slave." Lightning comes out of a dark-sensitive force users' fingers, not midichlorians. Midichlorians are simply a CONNECTION to the force. They don't create or define the force, only help their host to be aware of it. It is the will of the force-sensitive which actually affects the force.
And the Star Wars universe, despite it's many (theoretically) impossible technologies (faster than light travel, anti-gravity, etc.) is very much rooted in science. This is why certain sources explain how shield generators work while others have created entire stories about the companies that make the laser guns which are mounted on the ships that are never even seen in the movies... you get the idea. I think this is the reasoning for addressing midichlorians in the movie.
The term midichlorian is a clear reference, in my opinion, to mitochondria, the part of the human cell which supplies the cell's energy. Get it? Cellular power? Lucas was a great epic author but he wasn't very creative in his definition of ANYTHING. I use the terms Death Star (ooh nice name), Stormtroopers (a WWII reference), and X-Wing (a shape-named craft?) as examples. Hence, the inherent "weakness" of the explanation. (Lucas really wasn't that creative, and if you know a bit about the creation of Star Wars, you'll likely agree)
One more argument I'll shoot down: some said something about (I'm too lazy to quote everybody) it contradicting with the explanation's given by Yoda, Kenobi, and Solo. This is untrue. Qui-Gon is defining midichlorians, not the force.
So to offer my own answer to RebellionXXI's question "so why all the rage over the midi-chlorians?"
Because these enraged "fanboys" don't know what they're talking about. If they knew more about the force or midichlorians they wouldn't have their feathers ruffled by this explanation.