It has been a very long time (a year?) since I visited Wikipedia
without seeing any distracting notification on top of all pages. It is
either Wikimania, or a license poll, or steward elections, and now
about where Wikipedia will be in five years.
I do not doubt the need to inform Wikipedia users. I know that the
notification can be turned off (although it comes back if you go to a
different machine, your cookies expire, or the notification changes).
I would still request, however, that more restraint be used in which
notifications are posted and the amount of time they are allowed to be
on. Ideally, there would be no such distractions a half to three
quarters of the time.