The problem that I have come across with Service Broker (SB) is that there are other Microsoft technologies that provide distributed processing without the same licensing needs. If you distribute SB then you have additional OS and SQL Server licences. If you use BizTalk you have a richer system with similar licensing costs or if you use bespoke Microsoft Messaging (was MSMQ) processing then you have less.

The other options also appear to have stronger commitments of long term support from Microsoft.