I was looking for something more power than iCal to manage multiple calendars, with multiple tasks by Calendar and I found iGTD. Initially, iCal seemed just fine (especially if you manage a few calendars with a few ToDos).
However, I felt that I was being very limited by it’s interface when entering a lot of tasks. Also, there’s no way to handle tasks than become mini-projects or big-projects. After a while, the ToDos on iCal gets very busy and cluttered when it tries to auto-sort into “today”, “tomorrow” and dates.
So for now, I’ve been testing iGTD as a go between or rather as a front-end of sorts for iCal. I guess it’s still in its early stages and a pro version is due out soon. With iGTD, I’m able to enter tasks from the Menu Bar, and organize them into Contexts > Projects > Tasks. Next with one-click, I could sync it with iCal or my PDA phone, or both.
For example, I could enter a task for a sound project (Context), for the next show (Project). The Contexts on iGTD get synched with iCal with a prefix @ (alias) as a calendar on iCal. It’s also compatible with QuickSilver by Black Tree.
I still wish for a drop down calendar for the start dates and due dates on the tasks even on iGTD.
Finally, I use iCal as a hub for my calendars for subcriptions, publishing and parsing. Some of my calendars are on iCal and some that I jointly manage are on Google Calendars. So, I could subscribe to the Google Calendars on iCal, have them grouped and parse a combined feed to someone by calendar group!
By the way, I’m still on Mac OS Tiger.