Resource usage, responsiveness. They did a lot of good under the hood work with it. Just metro ... make all the good will that would have been won go to waste.
Yes I was so mad when Windows 8 came out because of Metro and I thought if they had just released something that looked like Windows 7 and said, "We made it leaner, we cut the boot time by 40%. Shutdown is faster too and we made over 200 smaller improvements to make things easier." I would have happily said, "Where do I buy?"