Have just been looking at my notes from TechEd at Barcelona and one of the things I remember was from one of the BizTalk sessions where BizUnit was being dicsussed.
I was shocked when there was a show of hands among BizTalk developers and architects and about 80% of them had never used BizUnit. It makes me wonder how much of a nightmare some BizTalk projects must be due to people not testing their BizTalk solutions properly.
If you have never heard it stop everything you are doing and go to the following site right now:
http://www.codeplex.com/bizunit
Ok rant over!