Google just announced that on June 1, 2012 it will end support for Google Sync for BlackBerry. If you already have the app installed, you’ll still be able to use it; however it will not be available for download after June 1.
Google recommends that you use the BlackBerry Internet Service (BIS) or the Google Apps Connector for BlackBerry Enterprise Server.
Instead you can use a much easier solution: AstraSync! Compared to BIS, AstraSync gives you the added benefit of full two way push sync of Gmail, calendar and contacts to your BlackBerry.
For full details of how to configure AstraSync to access your Gmail, calendar and contacts on your BlackBerry can be found on the AstraSync Website.
EDIT 2013-02-23:
It looks like Google have decided to leave BlackBerry and other smartphone users completely out in the cold ending support for the ActiveSync service on Gmail. More information can be found here: http://support.google.com/a/bin/answer.py?hl=en&answer=2716936&topic=27549&ctx=topic
AstraSync 
It’s too bad Google is ending support for Google Sync. The Blackberry Internet Service (BIS) unfortunately does NOT provide a better overall experience. It has at least 2 bugs with its synching that do not exist with Google Sync, which make the BIS solution non-usable for me. One moves additional first names to the last name. And the other duplicates address information to the “address 1” line.
I’ve posted full details about them in the Blackberry Support Forum: http://supportforums.blackberry.com/t5/General-BlackBerry-Functions-and/Name-amp-Address-problem-with-Blackberry-BIS-sync-for-Gmail/td-p/1869287