As someone who has direct experience in the EU institutions, I would probably vote out. It wouldn't be with frothing glee though.
Within the institutions, there is massive resistance to any kind of reform or change. There is also incredibly little foresight, which can be utterly mind boggling at times. Not all departments will be awful, but it isn't a minority. Of course, you get some absolutely incredible, brilliant, mind boggling clever people working in Brussels. But that doesn't mean the system they are working within is any better.
If we vote to stay in, the UK will be told in no uncertain terms "you voted to stay in. Your people are happy. Therefore stop complaining and just do as we say". That's honestly not an exaggeration.
And really, the EU isn't very democratic. I don't think anyone who has worked in the European Parliament could argue otherwise. Likewise, the biggest player in putting together legislation is the Commission, and citizens get literally zero say in their appointments.
TalkinPease - I disagree with you actually. Although the Institutions might be very angry with the UK, and there would be some necessary public condemnation from others to appease Brussels, really there's no reason for any resentment between member states. If anything, France, Spain and Poland will be very keen to maintain good bi lateral relations with us. Exactly how many citizens do you think are living in the UK from those places? With employment in those countries at such dire levels, they will be keen to avoid a sudden influx of expats.
Why on earth would countries suddenly introduce visa requirements? It doesn't make any sense whatsoever.
Why would France remove security from the borders? That's not subject to an EU agreement.
What the UK would look to do (I imagine) would be to negotiate very easy terms for northern/western european citizens to come and work in the UK, and introduce very strict requirements for poorer (most likely Eastern) counterparts. These would obviously be reciprocal, because that's how negotiations work. The EU as an entity can't get involved in bi-lateral relations, so wouldn't really get much say.