Well, I don't mean to be a wet blanket, but elections not synonymous with democracy or freedom, nor do the latter two necessarily follow from the former.
Elections are just the most visible aspect of democracy, but there are many other things a democracy requires such as rule of law, respect for minority rights, free press, civic responsibility and so on. In Iraq these things are either nascent, seriously challenged, or non-existant, and their development will not necessarily follow from a "successful" election. The Whitehouse formulation of 50%+ turnout equating with success contains some serious misdirection. After all, the Shia are going to turn out it record numbers not because they respect democratic principles, but because it is a way for them to gain power over the Sunni minority. This is not a healthy foundation for democratic development.
In my opinion the election will likely change very little. The voters are not selecting individuals, or even parties with distinct platforms, but broad "lists" whose positions on specific issues are largely unknown. These lists will then among themselves select who will run the country. It's very probable that Iraq will end up with much the same government with most of the same people as it had prior to the elections, the Sunni will remain alienated and dissatisfied, and the insurgency will continue.
The big change will be for Washington, as elections will be a significant PR coup for the administration, and will allow it to portray its mission in a more positive light. As for Iraq, if things turn out well elections may be a step towards democracy, but it'll be a very small step.