Yeah, two way sync would be nice. Unfortunately, the iCal subscription format is one-way by design.
We would have to create an application that ran on your computer in the background and hacked into your iCal database and synced it with Toodledo. I'll add this to our to-do list, but we are web programmers and don't currently have the skills to do desktop programming. Maybe in the future we'll find a talented genius who can do this.