I'm usually around 2:55-3:00 for the marathon in my training shoes. I'm considering the Nike Zoom Streak but I don't want to invest $120 in shoes that aren't worth it. There has to be a trade off between the advantages of lighter weight and the disadvantages of more pounding absorbed by the body due to less cushioning. I'm worried 26 miles may be too much pounding and negate the weight advantage. Are racing flats worth it for the marathon for someone in my time range?