I applied SP1 to Exchange 2003 last night. Today I noticed I was not getting any local mail. I used google to find a thread that recommended re-applying sp1 because store.exe was probably still at the old version. After applying sp1 and rebooting, the mail got delivered after a couple minute delay. I did not find any error messages to help my debug the problem. I did confirm that store.exe had not been updated the first time I applied sp1. Oh well!