I thought I was the only one! I updated to Mavericks the day it was released and when I reboot and get to the start up screen it takes forever with the spinning dial before I get to the main screen. I did verify and repair disck permissions through disk utility which seemed to help a little bit and I checked to see my memory usage and It looks like that may be the issue. With only 4g of memory it will take it longer to reboot.. I'm hoping there is an update for the older Macbooks.