Yes, it seems that this IS widespread because we are experiencing the same thing here in Sweden.
For me I my instant notification was working and I received email until I disabled my notification, because I knew I wouldn't be able to run out and FTF anyhow. That was like in November. In March or so I Enabled the same Notification, but nada. I even tried changing my email address.
I've tried both my own domain address AND my gmail address direct, same result: no notification.
As a premium member I'm pretty perturbed! #-|
Please look into this and fix it Groundspeak!