It's getting quite a bit of users, and the average session length is 14 minutes. Quite interesting :) I love it. It's sort of like Gmail, minus the notifications through my phone (which is a good thing, because it would be way too spammy). I can rest assured that when I visit that tab, I see the latest stuff. No refreshing or checking both pages. I have them both, always up to date, and at a glance.