The issue is this one: I would like to use exclusively beta.mb.org.
However links in my subscription mails, links used in forums, wiki, IRC, all points to mb.org.
So if I really want to use beta.mb.org, I have to edit URLs each time.

But if mb.org was automatically redirecting me to beta.mb.org because of my user preference, it would work nicely.

IMO until something like since is done, beta.mb.org won't be used intensively, which is a shame.

Note: I could (and maybe will) hack some userscript, but I think this should be addressed more generally.

If anyone has a better idea, feel free to suggest it