Racing Flat running shoes are the ideal choice when you want speed over a shorter distance.  Believe it or not, halving the weight of your shoes will generally lead to a faster time - small though the difference will be in comparison to your own weight.  Finding a more efficient foot strike is easier with a lighter shoe also - you can feel every step and it's easier to feel the position of your foot strike.  A faster running cadence comes more naturally because it's easier to lift your feet.  They are ideal for temp training runs and race day.

The downside is that they are not great for everyday running - they do not give adequate protection if you are pounding the concrete daily.  They also wear down faster - the EVA midsole is thinner and you will notice more readily as it becomes worn.