I don't think there's a bug. I was testing today on my local host which is the latest version of 2.5, but I've been able to see the upload multiple files in a .zip on our production server since it came out.
Hate to repeat the usual, but clear the cache, don't use IE or Safari. Force a refresh (in Windows Ctrl-R).
Oh, and you might also experiment with demo.moodle.net to see if you can see it there. I just tested, and yes I can see it there when logged in as Terry Teacher. I added an Assignment, ticked the feedback files box, and could see it.