The anime follows the manga pretty much word for word, at least the bits at the start that I've seen. - MoonShadow
Note also that AdventuresOfTheMiniGoddesses exists, wherin miniaturised versions of the goddesses have adventures, mostly involving the rats who live in the attic. Actually, don't note it, and forget you ever heard about it. Episodes clearly subscribe to the TwoMinutesOfCrack theory.
Anyway. The story alternates between two forms.
First, the hilarity caused by having a harem of goddesses (and half demons, and monsters and rivals and... you know the general story. Goddesses emerging through the bathroom mirror, demon sisters trapped in the TV. Main character devoted to them all, and Belldandy (the first godessess) utterly in love with him. And innocent and naive and being stepped around by her sisters, who alternate between trying to break them up and trying to cover up a perfectly innocent event that they misread.
The other half of the story involves the sisters using their powers in strange ways. Winning the (car) race so that the club can keep the clubhouse. Debugging the celestial computer system (with a mallet), trapping demons with polka CDs. Fighting off the end of the world.
Its all very silly, very well wrapped together and DEFINITELY warrants its class five WAFF radiation source warning.
Its main benefit to the world was as the inspiration of [Dire Fates]
I have.. heard of this evil. It cannot possibly be any worse than the SailorMoon / Constantine corss. Which I see is by the same author. Evil and obsessed. Run.