My opinion on it currently is that it looks promising but it's quite useless until there are finer controls on when and how cards appear (the controls there are now are really simplistic), and more importantly the ability to create my own cards, which would give me a reason to get back into SL4A.
As an example, the commute card that shows your distance from work/home is nice, but I have two jobs and commute home->work->work->home. I'm not sure I expect Now to figure that out quite yet, though it wouldn't be hard, but I do expect to be able to teach it that, which I can't currently do.