My experience:
1) submitted my signup details, the page never returned a response and just hung there, but I did receive an email and was able to login
2) There's no difference between "add item" and "insert after" on the last item - but there is no way to add an item to the start of the list. I have to insert after the first item then re-order
3) I could never use this on a daily basis but I could really use it for week-to-week planning, especially if it had an API
4) As such I would prefer gcal style dragging/gantt style blocks
5) If you could create a simple "time block allocation" tool I'd pay to use it.
The use case for me would be to plug my task system (for which I actually use my own CMS where I create pages for each "sprint"). I currently use Google Calendar but the API is kind of hellish and I've never gotten around to using it.
The fact is that daily planning revolves around a few things for me: things that arrive in my inbox, things i'm supposed to be working on (time blocked off in google calendar) sales/follow up tasks (I use highrise, this comes under "things that arrive in my inbox") and appointments (for which I use google calendar).
I then timesheet everything via an IRC chat room (as do my colleagues).
All that's missing is an elegant interface for blocking off time for tasks, being able to rearrange them and then export all the information via an API so that I can see directly how scheduling is affecting my cashflow without having to update a bunch of spreadsheet data.