i'll leave the immigration conversation aside as that is very well covered in the media & I believe that is a small token of what is at stake here.
EU has been around for the past 17 years, initially with member states that were "reasonably" comparable to eachother (lifestyle, democracy, laws, culture?) - and in that time it has hardly been a success, i'd call it a massive failure. Now that it has been extended to accommodate new member states I for one don't see how it can ever work.
I remain unconvinced that we need to be part of the EU in order to trade with the EU, not to mention that we as a nation should be & are looking to extend our trade relations beyond the EU - with special relations with China as an example.
Finally and more importantly - this is about our sovereignty & democracy, I don't see any reason to hand over our power to a bunch of unknown unelected unaccountable bureaucrats in Europe - regardless of the financial outlook if we were to pull out.
With that in mind and having read the views on this thread - I remain in the OUT camp.