Looks good! I'm using HabitBull[0] for past few weeks, and it's not bad, but i like your approach, so i'm going to give Grow a try.

Few random notes after first minutes in the app:

- i made a typo in the habit name and couldn't find a way to edit it

- it would be useful to have an option to check the relevant days for each habit (eg. only mondays, exclude weekends, …)

[0] http://www.habitbull.com/, got a link from some HN comment i believe