Bill sez: "To me, the only sequence that's actually puzzling is the Room At The End."

That's the Kubrick mind f**k, alright. I'm not sure that any interpretation is necessarily the right one.

How about this: The room is a womb for the star child, and Bowman is the zygote. Bowman witnessing himself age is a visual metaphor for "editing" the remainder of his human existence down to a short period of time before he is reborn as the star child (apparently he returns to Earth as the star child shortly after he left it, so he could not have aged normally). The advancing stages of aging represents the development of the fetus in the womb.

Of course, it could be something else entirely.