Speaking of which...
While using an earlier version of pound (2.4.2, I think), I initially
used sessions to send the user to the same server, not because it was
required by the app, but just so that if I'm in the process of updating
servers, the user doesn't see old_page -> new_page -> old_page.
I found that when I disabled a backend, the user would just get error
pages, they wouldn't be switched to a new backend.
Has this been fixed? Or is it not considered a bug?