Yeah, maybe not. How about telling the user to disable the -Devel/-Testing first before running that and leaving only the stable repositories and CSSU on? If you want the user to come here whining, that he's broken his N900 then sure, go ahead and tell him to do that.

I'm just saying this, since it pisses me off that everyone thinks this solves the problems. It doesn't, and as mentioned before, it can cause more problems if wrong repositories are enabled.