It would be the same thing as if he said your ears speak to you, and tell you what sounds are happening around you.
There isn't one example in the saga of a midichlorian's sentience on it's own. In fact, the supposition Qui-Gon has that Anakin was created by the Midichlorians is questioned by the idea that Plaguis and or Palpatine may have in fact caused Anakin to be.
Also, the Force in the classic trilogy is everywhere, just as it is in the prequels. What's happening is the Jedi noticed a co-relation between powerful force users and higher midichlorian counts. They know not everyone who tries to become a Jedi succeeds, so they started hand picking candidates based on their Midi-Count. Obviously they also decided that attatchment was a bad thing, which is just another reason why they would want to pick their candidates so close to birth that their propensity to use the Force wouldn't be self evident.
I think I mentioned this before, but in the ANH novelization, Obi-Wan tells Luke about how the Republic tried to define the Force with science, but that they never quite could. That perhaps there is just as much magic as science in the Force.
To me the further layers only underscore how the Force had already been portrayed up until this point.
Also, I don't know how you could say they Force was only vaguely hereditary in the classic trilogy. If it wasn't -very- hereditary, then the Jedi couldn't have been all but wiped out. Force users would be popping up naturally out of the population like a sick game of whack a mole for the Emperor. And the only reason they gave for Luke and Leia being strong in the Force was due to their lineage.
The Force is still everywhere, it's just living beings have Midichlorians that allow them to commune with "the Force". Wether the Force itself has a will in the first place is a point of view. Obviously Qui-Gon sees the Force as having a will, and he feels that when he quiets his mind, the Force will show him what it wants him to do through the Midichlorians, but it's still his interpreation just as we might take a coincidental happenstance as "divine direction" of some kind here on Earth.
I hear some of you saying "nothing is sacred" to Lucas, but I don't see how he has changed anything about what has come before.
Not one little bit.
Midichlorians do not explain the fantastic abilities Jedi can call upon, it merely adds another layer to the mystery of the Force. I think it's much more well rounded to present both the mystical and the scientific side to the Star Wars universe. So many people seem to treat science and religion as 2 separate things that contradict each other, I personally see them as 2 separate approaches to the mysteries of life that co-exist without contradiction. Religion and Science both present theories that guess at the mysteries of life, the only difference is science is the attempt to figure out more about the secrets of life through tangible tests that can be verified, while religion attempts to understand the secrets of life through "what sounds best" or "belief" without proof.