The deed is done. Václav Klaus has signed the Lisbon Treaty and thus it becomes enacted. (BBC News: Czech leader signs Lisbon Treaty) Now it is no longer a question of "if" but "now what?"
Inevitably attention is now going to turn to the UK Conservatives as to what policy they will follow if the next election puts them in government. The wilder ends of the blogosphere are already demanding a retroactive referendum be held early in the new parliament in the hope of undoing things. But let's be clear - such a referendum that votes "No" can have no legal force. The changes can't be unenacted.
(A slight diversion here as I expect someone is already about to post a reply on the lines of "Yes it can be undone! Parliamentary sovereignty means anything can!" Parliamentary sovereignty is all well and fine on matters within the full jurisdiction of Parliament. But it doesn't apply to areas beyond the scope of the jurisdiction or where jurisdiction has been withdrawn. For example Parliament could repeal the Canada Act 1982, but try enforcing that withdrawal in Canada! Similarly Parliament cannot undo an action transforming the EU, anymore than a person can unscramble an egg and put it back in its shell.)
All a post-ratification referendum would do is consume a lot of time and taxpayer money for no discernible difference. At the end of it the United Kingdom's relationship with the European Union would remain the same no matter what.
There are only two real ways forward. One is to grin and put up with the situation we have. The other is for a new government to undertake a renegotiation of the terms of membership of the European Union and then put those terms to the people in a referendum, much like the 1970s Labour government did, and if a satisfactory arrangement cannot be found then to withdraw.
However too many on the Eurosceptic wing of the party are rarely realistic on these matters. They have just spent the last four years focusing all their energy on the rather trivial matter of which grouping we sit with in the European Parliament after all!