Mort,
Actually, the question is not often asked. As an instructor, I have found that students come to the rebreather class with the expectation that bouyancy is a "given", and the rest of the information is what they need to learn.
As it turns out, the first few dives on a rebreather are very humbling, with lots of fumbling about and crashing into things, like the bottom!
This brings about sort of a sudden depression on the part of the student. They begin to question themselves, and the choice they made to come to the "Dark Side" and to take up diving with one of these "damned infernal machines"!
Interestingly, the better the student is, as a diver, the worse the depression gets. I taught a student recently who was, and is, one of the best divers I have ever had the pleasure of diving with. He is a diver with great experience, and is a Course Director for a major training agency (not PADI).
He was thoroughly and utterly disgusted with himself at one point, but we worked our way through it. I encouraged him, and ran another dive where we worked on the bouyancy problem. It was really fun to see the light come on, and to be able to say: "By George, I think he's got it!!!
"
As Rigdiver says, the essence is to keep the gas in the various spaces down to a minimum, to minimize your management problems. Work to get your trim EXACT. And be of good cheer! Keep working at it. The light WILL come on!
Rob