Hmmm.....first thoughts: very interesting. The title is the reason I clicked on this as I'm Christian, but that isn't a prerequisite for me to enjoy a piece of music per se. Not sure if the title does fit though. I don't really hear the rejoicing. The tone sounds a bit more mysterious and eeriness which creates in me a feeling of indifference. Since I listen to the piano a lot, I'm not a fan of the tone of the piano you used. I would of liked some human feel to it as well--sounds a bit too midi.
It is ambient like, and I think it works fine as such. Can't say I enjoyed it completely, but you still got my respect for it.