[Brian]

Needless to say, the current situation Calendar/ToDo situation is a little muddy. Some of the features that Apple's adding in iPhone OS 4 will help us clean this up a bit. (You won't be forced to create a calendar to get reminder alerts, for example.)

Mac OS X: has a ToDo database, and a Calendar event database, which are both shown in iCal, though the ToDos are separate from the calendar.

iPhone OS: Calendar app shows calendar events, but not ToDos. If you want to pop up reminder alerts, you have to create calendar events to do it.

Meanwhile, Blackberries and other Non-iPhone smartphones sync with both ToDo and Event databases through third-party utilities. (We added the to-do support as a way for folks to sync OmniFocus with a Treo, for example.)

If what you need is the ability to see your ToDos in the calendar view on your Mac, though, you may want to look at BusyCal - it does that.