AWSOME! So all i gotta do is use the happiness berries on my guys until they no longer have any IVs.

I heard there was an IV cut off line. Like once u have 100 IVs in a single stat your stuck with that stat and their aint no going back from it... is that true?

Do the happiness berries work in D/P?

I would assume someone could check this with us by having a level 99 pokemon and useing one of the berries on it and then a rare candy, then turning it off doing it again without the berry and see if there was a change.

Could someone test this please?

'IVs' or DVs are your pokemon genes, the don't chance and are unique to the pokemon. 'EVs': effort values, are reducable by berries. if your pokemon had say, 150 EVs in a stat and you used a berry it'd be down to 100, meaning it can take no more that 11 berries to lower a stat to 0 DVs.
IE: DV's are no permanent if you have lots of berries.

Yes they work in DP. You might notice, on the description of the berries, that it says it reduces the base [stat]. It actually reduces the EVs. If your pokemon doesn't have any EVs in that stat, it just raises happiness.

Yes, you can completely reverse a pokemon's DVs from 0 even if they're maxed, and they DO work in D/P. They grow there, so why wouldn't they work?