One of the most frequent topics we deal with when migrating a user to Google Apps is whether or not a Blackberry device will work with Google Apps. The quick answer is YES! The long answer is 'Yes, but not quite as well as an iPhone or Android device due to the lack of direct integration with the device'...
Blackberry devices have always been tied very closely with the Blackberry services provided by RIM, the company that makes Blackberry devices. The Google Apps service does not have the same capability to integrate with the Blackberry device as the standard Blackberry email service (such as Push email), which presents a challenge to users of Google Apps and Blackberry. The Google Apps applications and data normally used on mobile devices like email, contacts and calendar are available on the Blackberry via add-in applications provided by Google. These applications give you access to your Google Apps data thru various Google tools on the Blackberry, but they are not something that come installed on most Blackberry devices. These applications are very easy to install and setup and usually require only a simple download and entering of your Google Apps account information once. From that point forward, your Google Apps content is accessible from the Blackberry device including email, contacts and calendars.
With iPhone and Android devices, the level of integration with the built-in applications (like Mail, Contacts and Calendars) is more direct, and does not require additional applications to be installed.
You can view all of the available add-in applications and instructions for Google Apps on the Blackberry device at this page: http://www.google.com/mobile/blackberry/
*** PLEASE NOTE: In order to install the native GMail/Google Apps Mail application on your Blackberry, you must visit m.google.com/mail from your Blackberry device.