I went through the same exact thing on the first day of day care @ 2.5 years old. However, I don't think he suffered as much as I did because..... he loved it and has never looked back.
I saw this article today and it made me feel good about my decision although it pertains specifically to Pre-school, a good day care is preparing your little person for Pre-school
http://abcnews.go.com/US/t/story?id=13803174