I have just spent the day debugging the ASP.Net Membership provider as I had an issue where users could not log into the my test server.
I was able to debug through the membership provider and find out where things were going wrong.
As it goes the error was due to my own stupidity, aren’t they all, but it saved me hours.
Another Red Gate tool that has become a permanent part of my development tool kit.
I have to mention that SQL Compare is also excellent.