Where I live, the cutoff date is October 1st. My dd's birthday is October 29th. I don't personally have an issue with the cutoff, even though dd's birthday is close and she will start k when she is almost 6. She is smart (academically), has great fine motor skills, but is still socially a 4 year old --and that is why I am truly glad that she will wait a year.
In our district, children who have birthdays from about June to the cutoff date are screened before kindergarten. Many of them go to junior kindergarten, which is a transitional k program for children on the young side of 5. It has worked wonderfully in our district.
I used to teach kindergarten and first grade, and I really noticed a difference in waiting a year. The social/emotional and fine/gross motor stuff doesn't seem major in the beginning, but by first grade it was. Most children recommended to wait a year (who waited) really excelled. Those who did not (but were recommended) usually had some issues that were mis-labeled as learning disabilities--things that were really developmentally normal (for their younger age).
Anyway...I digress.
I really support a cutoff. There has to be one somewhere, and it really does need to be adhered to in the public school *as it currently runs*--I stress this because the public school is (unfortunately) not designed to function with multi-age classrooms. As a former k teacher, there is a vast difference between a child who is 5 years on the dot, and one who is 5 years and 6 months. With one teacher, 20 kids, no aide, and a non-individual curriculum (again, unfortunate), it is truly in the best interest of the child to wait a year to start.
Hey, consider this...a child who waits a year can always benefit from: an extra year at home with mom (doing challenging thing that make sense in their own world), attending preschool, and just being a kid for an extra year.
Sorry...I really rambled.