Thinking about building your own AppDomainManager?
If yes, then don't forget that it need to run in full trust, so adding it to the GAC is something to keep in mind...at least, that was what i've ended up discovering after spending 2 hours trying to understand why i was getting an exception when the 2nd domain tried to create the custom AppDomainManager i've written. btw, if you're into this type of things, you need to have this.