When questions have been merged/migrated to another trilogy site, it would be nice if the page still showed that it was migrated, but include a bar or some other indicator that said:
Please wait: Redirecting you to Super User/Server Fault/Stack Overflow/Meta in 3..2..1..
and automatically redirect the user.
This would also benefit users who are in the middle of answering a question. Rather than get a "Page Not Found" when they submit their answer, are brought to a page that shows it was migrated and then are automatically redirected to the appropriate new home of that question
UPDATE (4 years later): Looks like a HTTP 301 would be a good idea.