Adding tasks & linking them as dependencies is very cumbersome. It makes you go 3 or 4 screens deep to select the predecessor task from a list. By that time, you may forget what task youre looking for. Fail. The minimum duration for a task is one day. So you dont want to work with complex classes that represent Time Spans. How about Decimal? Maybe you just cant do project planning on an iPhone. At least it was on sale.