I enjoy having a separate place outside of the calendar to see just birthdays and anniversaries for my contacts.
Although, it no longer supports FB sync & messaging from app. (And thats a FB thing):
After trying 5 other birthday apps this one is the best!
Imports all events from Contacts (birthdays & anniversaries, etc.), lists them in a very legible chronological order, separates them by month and allows you text or phone them from within the app. Different color themes are available and all pictures stay updated.
The alert choices in this are the best!!! For some friends, I only need notification same day and for others I want more notice for gift giving.
Keep it going! Nothing else compares.