If you entered here, most chances you loved previous encarnations and so your demands are mediocre. However for those who want better performances for their cheaply-made-by-slaves luxurious running shoes:
I can understand why Asics Kinsei are expensive, why Mizuno Prophecy are expensive etc'. But the Glycerin line is just a normal 80$ NB shoe with luxurious upper, there's no premium cushion at all. I don't think it healthy to run with such low amount of cushion.
Use only with good orthotics, preferably rigid or extra rigid. While there are new brands like Hoka One One which offer substantial amounts of cushion for the Premium category, brooks stays behind. They improve weight (bravo..) but not cushion firmness (rebound).
Brooks definition of 'Neutral' is too fluid. For 150$ you must be innovative, those shoes are not.