Just completed the Google Latitude setup on Blackberry Curve. The process is very simple. I was already using Google Maps 2.0 and just had to download the latest version of the Google Maps and install it, which comes with built-in Google Latitude.
The Latitude is completely opt-in right now and you need to have a Google account and approval from both parties to see each other’s information. A public interface would be good if someone wants to share the location openly on blog etc.