I wish Britain had been wise enough to reject membership of the European project back in the 1970s. With the Westminster political parties sporadically committing to future referenda on EU treaty changes, perhaps we will have an opportunity to correct this.
There is much about the EU that irks me, and I'd certainly be wary of much closer integration (and was averse to joining the Euro even before the recent meltdown), but on balance I'm in favour of the UK's continued membership. Leaving would be a big mistake, I think.