Rich,
I just wanted to point out the Canada US analogy doesn't work. There's no chance of an union and furthermore we still maintain a parliamentary system based around the same Queen as you.
The analogy with Quebec and Canada is a much better one. They have had multiple votes to separate, but none have been successful to date (one was very close). It's thought that immigration is now becoming a series the factor in Quebec not being able to achieve independence in the future.
There was a pretty comprehensive independent study done around of the one votes that concluded both new countries would suffer economically in the short term. It was a pretty rationale argument that touched on duplication of services, initial confusion both internally and externally, increased cost of debt because of debt rating reductions and the cost of sorting out the complete separation of to new governments (that was actually worked out in detail in preparation for a vote that most thought would be successful). The obvious was there would be a lot more for Quebec to do from establishing a wider infrastructure to cover national programs through to writing a new constitution and laws.
The biggest unknown that cropped up was whether other areas were free to have their own vote to stay in Canada. The native communities were the most interesting aspect of that secondary debate. As we got close to the last vote (assumed to be a successful independence vote) the level of complexity around the issue increased as they (Canadian Federal Government and not Quebec) tried to get all the ducks in order to make succession smooth.
It was an interesting time as politicians allowed the process to go forward and the federal government stayed largely out of the way. In frustration, normal Canadians became very active in campaigning for Quebec to stay. It had a remarkable impact on the process. Quebecers who wanted to remain went from quiet to vocal and the entire dynamic flipped mid process. I always thought this vote was very good for "Canada." Whether successful or not, the relationship between countries will have changed.