If this allowed anonymous analytics in order to discover and suggest useful rules, either at the personal level or in aggregate over all users, that would be awesome. Likewise if you can publish, clone and fork useful rules then modify them for one's account. The less a user has to come up with their own rules, the better.
And there are things that IFTTT doesn't do for e-mail that this might do. And there are API's that IFTTT doesn't support (the big one for me is springpad).
As for time sensitive, this could potentially learn what you respond to immediately upon viewing, and what you wait on or don't view, (and even analyze that as a function of day, time, sender, etc.) If it had permissions to analyze e-mail texts and had enough users, it could use machine learning to learn what phrases were likely to prompt immediate action, IE "By tomorrow morning" vs. "By Tuesday morning" on a Wednesday.
As for non Oauth accounts, A browser plugin that stored your credentials locally could still be possible. I seem to recall reading about somebody working on a clever way to do this involving passing session information using a proxy and encryption or something like that, but my memory isn't great.
All in all, I wish them luck.