I’ve heard this around quite a bit lately, but I attend some conferences and follow a lot of newsgroups. If you haven’t heard:

Database Mail (was also called SQLimail I beleive) the new SMTP mail service in SQL Server 2005 uses Service Broker as the underlying infrastructure. One of the reasons why is: scalibility – “Database mail provides background or asynchronous delivery”. Also listed are security, reliability, and supportability. Hmmm…

That brings the number of internal features implemented using Service Broker to three.
1. Event notifications
2. Query notifications
3. Database mail

One slide I saw (I forget where offhand) said “look for more in future”.