IIS6 Has a fancy new feature called web gardens, this helps keep the uptime on a site.
For those of you who write websites and have generally only written for a single server (there are people who do this, intranets, small sites etc) then you have to bear in mind that this makes your application work like a Web Farm. If you store stuff in Cache or Session or Application, there are (N) copies (where N is web garden number) all seperate from one another.
Having seen the setting for web garden in the Application Pool and realising its impact, its a little too simple to change, now help text, no warning (“did you design this application for split deployment ?”).
Just a thought.