I think that Chi and Ki and 'Energy' in some of the neo-pagan senses are all talking about some similar objective territory. I've done both Chi exercises and various 'energy raising' rituals when I was playing with various forms of paganism. The experiences seemed to have a lot in common.
My personal opinion is that:
A) There is something going on. It probably doesn't directly relate to 'energy' but that's the closest word we can find to associate it with... or at least it tends to be the most common one. I think a lot of it has to do with the neurological aspects of our reality, but I think that's a pretty huge chunk of reality anyway
B) The less symbols dumped on top of one of these systems, the better it seems to work. That is, I could feel that internal 'energy' when in ritual, I could feel it more when practicing Chi and I noticed the feeling quite a bit when playing with Antero Alli's 'Archelogy of the Soul' where he basically tried to strip of all the metaphors and work directly with the psychological mechanisms of ritual.
So, in my wild conspiracy theory:
Once upon a reality, humans found that they could control their bodies much more competently than most people believe today. To gain this control, certain exercises and meditations were useful. In order to teach these, people created models/maps/symbols to make teaching easier. Over time, the map became the territory and people became so focused on the signs and symbols, that they lost sight of the actual valuable stuff. And thus we have the birth of religions, invention of the idea of Magic and Supernatural and Powers...
Of course, I don't believe this... but sometimes I think about it. I agree with Kai, when I do Chi (or some rituals) something definately seems to be going on... and though I am trapped in my perceptions, it does tend to act as though its something beyond simply psychosomatic response.
I don't think energy is really the right term, but I dunno what the right term is.