The app looks quite nice (and useful). I'd install it instantly if it was free. But it's not. So I guess I'll just settle for my usual online access. I'm almost always near computer so it's not that crucial for me to have it on my iPhone.
But for people on the ago and in need of total control - this can come in handy.
I haven't bought it yet myself, but have heard good things (and the site definitely makes it look good).
It's a shame Google can't roll out this sort of interface itself though - just as a webapp. It's done pretty well with the Gmail one.