Firefox came to our world 5 years ago and how big of a difference did it make!
For me it wasn't easy but I was able to convert more then 75% of my users off IE and onto Firefox.
I was never able to make the Firefox adm work in my Active Directory environment so I had to find another way.
Chris Ilias wrote a Locking Mozilla Firefox Settings manual in his blog. The concept is changing the preferences to the template you need and then locking it into a new Mozilla configuration file.
While I wouldn't recommend this for a large environment, This is an easy to implement way that provide!