OY, I didn't get to finish typing my question. I've paid for Premium and have been able to get my tasks to show up on my iCal and Google calendars, but not on iPhone calendar. Downloaded app on iPhone this evening. What am I missing out on? Thanks!
In order to display your tasks on the iPhone calendar, you must subscribe to the iCal feed just as you did with the Google Calendar. You can find a description on how to do so here: http://blog.fosketts.net/2009/06/17/subscribe-internet-calendars-iphone-30/ on iOS 3 as an example, but any later iOS version should have an option to add an iCal feed (probably through the "Add new email account" feature).
Woohoo! It worked. My Todoist task are showing up on my iPhone's calendar (iOS6). I added the iCal feed under Add Account>Other>Subscribed Calendar.
Glad to be back to using Todoist after not using it since 2008 or so. You've come a long way since then.
Thanks for your help.