Many Canadians have become frustrated, according to polls, with the fact that we had a federal election in 2004, 2006 and 2008 and could well have another in 2009 or 2010. At the same time, many have expressed dismay at the fact that the Green Party got 6.8% of the vote and won zero seats, while the Bloc Québécois got 10% of the vote and 16% of the seats.
Unfortunately, these two frustrations are largely incompatible. Though we might see the Greens win a seat or two with instant runoff voting (a model I support), it would not result in proportionality between votes and seats.
The reason we have had all of these elections is because of minority governments. With a system of proportional representation, the last time we would have seen a majority government at the federal level in Canada would have been 1984 when Brian Mulroney won 50.03% of the vote and before that 1958 when John Diefenbaker won 53.66%. Not even Pierre Trudeau's big sweep of 1968 won a majority of votes - he scored 45.37%.
The situation in Israel today is not dissimilar to that which we saw in Germany in 2005. The votes are spread so widely and the two "major" parties are so small and close to each other in size that the only option for government is a grand coalition of the major parties, which are forced to govern with a narrow set of objectives based on the few policy areas where those parties can agree to compromise.
This is no way to govern a country. We must have either majority governments, coalitions of like-minded parties or minority governments with a commitment from other parties to keep them in office for some time to have stable, effective government. If you ever think we could make all of our problems go away by bringing in PR, I would direct you to look at those countries who already "enjoy" that system of election. Based on the reaction of Canadians to the coalition proposal that came forward late last year, I would think that a system of PR would lead to a massive case of buyers remorse immediately following its first election.