Oh man, this was awesome! XD Love their personalities! And that you didn't stress the pace either, nor the details. The way the sun rays play behind the pillars, and the heavenly kingdom is presented, and God sitting in the bathroom... all of it feels polished to the point of perfection! Jesus Christ made an entertaining cameo too, and the story, that there needs to be a balance between the two worlds, it makes for a pretty epic tale to back up the comedy! About to head over to the second part soon and see how it fares there, though considering how much backstory there is it feels strange it'd be possible to end properly with just two parts...
As for the'defects' you mention: I don't think the pacing is bad at all, I feel like it lets you really savor the details, and the journey, though I do agree about the voice acting. If not else it feels like it'd add a lot with some characters voiced by someone else, so you can really differentiate between them, but at least having both God/the Devil voiced by the same guy, just with the same tone, that works perfectly. :)
Awesome work so far; onto the next!
-cd-