Top four reasons why you shouldn't care about the exit polls:
1. Non-response bias. In 2004, exit polls gave Senator John Kerry such a massive lead over President George W. Bush that Democrats began to prematurely celebrate based on what turned out to be unreliable figures. The same thing happened again in 2008, albeit to a somewhat lesser extent (Obama did win that year, after all).
2. Early voting. While the non-response bias may unfairly favor Democrats during exit polling, the disproportionate tendency of liberals to turn out for early voting could have an equivalent effect favoring the Republicans. Weighting and adjusting exit poll returns to account for early voting is an imprecise science at best.
3. They won't matter soon anyway. After all, it is the election returns that really make a difference - the law has never declared someone to be President of the United States based on exit polling results. While an obsession with polling makes sense in the days leading up to the election, it's a tad absurd when hypothetical results will be replaced with the genuine article in a few hours.
4. It brings out the worst in us. This may seem like an odd point to make, but it has to be said. Having been an active political junkie through four presidential election cycles, I can safely that I have never seen anyone react to exit polls in a flattering manner. Recipients of bad news will rend their clothes and beat their chests like medieval flagellants; beneficiaries of good news will strut and crow like obnoxious schoolchildren. It's just unpleasant.
While this last problem might be tolerable if the exit polls correlated to the actual balloting results or had a direct effect on the election itself, the fact that neither of these things is the case (see Points 1 to 3) means that exit polls should be dismissed as so much news static.