I sent my request an hour or so ago, but I haven't heard back. I thought maybe my email wasn't working (since it's brand new). So I sent myself a test email from my Yahoo email, and it works fine.
I'll keep checking it, but just wanted to know if it takes several hours or what.
It's done manually, so it depends on when someone has time to go approve join requests. Never takes over 24 hours, and all pending join requests were taken care of within the last 30 minutes, so you should have received a response already.