First of all, I wish to thank you both for taking the time to answer my question and elaborating upon it. It's very gratifying to have a place to go with these questions, and more gratifying still to actually get responses to them.
Now, to address the questions you posed in your replies...
What did you think enlightenment was anyhow? Something esoteric and mysterious?
No. Not in the slightest. If examples like Gautama himself are any indication, I'd expect it to be an increase in clarity when it comes to the understanding of reality. As you say, though, it does have a rather long 'tail' of preconditions. This is a structure I have yet to grasp fully, so I won't pretend to understand enlightenment.
I know there's a lot of ground to cover. I'll do my best to describe what I'm standing on with more eloquence.
Can you see all those sensations that make up those things come and go?
The state disappeared when I reached a certain level of fatigue (I slept four hours the night before I wrote the query, and something like five hours the night before that). It may have been unrelated, but it seemed to be a result of the mental capacity it would take to maintain it simply fading. That said, I still have a rather vivid recollection of the state.
I'd say the opposite, actually. All sensations gained a curious constancy. That is to say: I would find myself unaware of my breathing at times, but faintly (yet somehow profoundly) aware of the fact that I was indeed unaware. A sort of paradoxical feeling. This would shift back and forth; aware of breath, aware of lack of awareness of breath, aware of breath etc. Not on a breath by breath basis, but in intervals lasting a few minutes.
One more thing, that may be related: after the fading had happened, I found myself in another mystifying state. Somehow, I retained a little of the acuity the meditation had left me with. But everything seemed slightly surreal. I suppose I could illustrate it best with an example. I walked past a woman on the road while this was going on. I found myself observing every detail of her walk with an alarming
actuality. Like I somehow saw it all more clearly than I usually would. Yet I couldn't shake the feeling that her walk was artificial and false. That people don't really walk like that. This sort of perceptual game kept panning out for a few hours, until I receded into a quite normal state of overall tiredness.
Can you see the sensations that seem to make up an observer come and go?
This one is trickier... During the state described in my first post, I wouldn't say that's the case. However, during the following state, I found that my awareness would occasionally be drawn into the object. Like the observer faded, and the perception remained. Like the breath, this also fluctuated. Aware of not being aware, aware of being aware, aware of not being aware...
Serious troubles with family, etc rings of Dark Night, but order, context and more info would help.
I'll provide an elaboration on this in the near future. Right now, I'm feeling up for some rest.