Hi,
I did see those threads, but they didn't answer my question.
But, after some playing around I found out that this fail-over mechanism does work!
When you also want to do this, make sure you check the Event viewer / SQL Logs, that are the real errors. The errors .NET will give you are not descriptive and not always right.
Also, make sure you have the SAME user on each database. Not just the same username/password but also the same SSID:
http://support.microsoft.com/kb/918992/
Works like a charm!
Cheers,
Gab