1. When you do things on your list, they take up time. Putting them into a calendar view makes a lot of sense because you have to balance those tasks against the other time-based commitments you have (meetings, etc). When you have a separate todo list and calendar, it's difficult to get an effective view of how you're planning to spend your day.
2. I like the weekly time horizon. A day is sometimes too short to make meaningful progress, and a month is too long a time horizon to effectively plan. A week feels right - you can plan it out and make a dent in your project. But I've yet to see a todo list that lets you plan on this time horizon.
Potential ways to improve:
1. Sync with google cal to pull in my appointments
2. Show me time slots so I can plan my todos around my meetings