Not sure what to think, all I've heard from both sides is "This MIGHT happen" and "NO! PROPAGANDA!". Real lack of solid info.
One of the things that the EU has planned is something called TTIP though, which is gonna give US corporations authority over EU governments in a few ways.
Google it and have a read, some of it is frankly terrifying, so I reckon we'd be better off staying the hell away from that. Also as Mr.357 said, Turkey. A bunch of warmongers every bit as bad as the rest of the countries in that region, yet the EU and NATO play blind and bend over backwards to make sure they stay our sort-of ally. Even though they fund ISIS. Sickening.
On the other hand, the EU has done us some good too and some of the rules that govern all EU countries are probably a hell of a lot better than whatever the Tories would have planned without the EU to protect the citizens from them...
TBH when it was the EEC/common market is was already just as good as it needed to be, it was a simple trade agreement making sure EU countries and other paying members were all fair and untaxed when trading with one another. The very fact that the EU commission decided they had to make up some rules which had to be followed was already a bad sign of power going to head, even though I just said some of those rules were actually good.
And related to that last point, when Cameron went to the EU to try to negotiate a better deal for the UK, they flat out said no. Not even a negotiation, just another sign of power going/gone to head. If that's how they treat us when we're threatening to leave, then if we "vindicate" them by all voting to stay, they're gonna think they can do what they want to us.
All that said, I can't decide, I'm erring towards "out", but I'm not 100% sure about that...