Hi Wolfgang,
We use separate logging system in production to troubleshoot our BizTalk orchestrations, so that we can pinpoint what is failing when some BizTalk process goes down. The error messages in the Event Viewer are sometimes too verbose, and you have to dig in deeply to find out the root cause of what is failing and that takes time and effort. So, for us anyway, there is a tremendous benefit in having a separate logging system.
Cheers,
Daniel.