Here are some of the intersting points I came across while I was preparing for the Biztalk sever partner competency exam:

Point 1:

If you performed a custom installation including Development-only or Administration Tools-only, you must Join rather than Create a BizTalk group during configuration

Point 2:
You can upgrade from Partner to Standard, Partner to Enterprise, Standard to Enterprise, and Evaluation to Enterprise. You cannot upgrade from Developer to Partner, Developer to Standard, and Developer to Enterprise. Downgrades are not supported

Point 3:
Pipeline components should normally not be within the same solution as the projects that use these components, as the components get loaded by the pipeline designer and locked, so compilation would become rather hard

Point 4:
The master message box can only be scaled up but not out

Point 5:
When creating application ssomanage -createapps, in the application xml file set as follows

<appUserAccount>machineName\SSO Affiliate Administrators</appUserAccount >

Specifying any other value will result in Access denied error.