Whether you voted for Gore or Bush, I think that almost all of us can agree that the disenfranchising of over 20,000 black voters in Florida right before the 2000 presidential election was a national disgrace that we never want to see repeated. A BBC News article has some good information and if you want to see about 600 politically charged responses to this article, head on over to Slashdot.
Seriously: transparency and honesty are all important for a democracy. Inspection of the U.S. election process by respected international organizations can only be a good thing.
I just Google-searched for more information about this; the following two sites were the first two hits and contain material that seems reasonable to me:
Disenfranchising Blacks as Political Strategy
Florida's 'Disappeared Voters': Disfranchised by the GOP
PS. I just noticed that the OSCE was asked by Secretary of State Colin Powell to monitor the election. Also, Congress has recently passed legislation to clean up problems like we had in Florida - so, we are trying and international monitoring of U.S. elections is the next logical step.