I don't want to get into a discussion about whether or not we should invade Iraq. For the record, I don't think we should act without explicit UN backing, but those who think otherwise have valid points of view.
Steve is right too, though - the US and UK don't look like they are even trying to win hearts and minds.
The angle which I haven't seen explored is the medium to long term effect on the UN. It seems to me that we might be looking at the beginning of the end.
If the French veto military action, the US will go it pretty much alone if they have to. (They'll probably have British support, though Blair might, just might, take notice of the pretty much overwhelming public opposition.) This will leave the UN looking pretty irrelevant. League of Nations, anybody?
Of course, one has to wonder whether it's appropriate for France and Britain to have a UN veto. Russia, China, and the US, the superpowers, I can see - the UN would be meaningless without their support, so it's necessary to ensure that it never adversely affects their interests. But Britain and France's positions on the Permanent Security Council is a historical anomaly, reflecting those nation's pre WWII power.