Toodledo will import PalmOS Task archives: Toodledo : Palm PDA Import/Export.
So you can import your tasks to Toodledo, then sync them to your iPhone using either the Toodledo iPhone app or Appigo's Todo.app.
I've used Toodledo and Appigo Todo.app for over a year. Neither is perfect, but they're both a solid B+. I really don't know a better solution.
PS. How could they be better? Well, if Appigo doesn't make any more bone-headed changes to the Todo.app (they've mercifully reversed some past mistakes), and if Toodledo stopped deleting tasks > 1 yo and changed quick search to scan all task fields, then they'd be a solid A.
Update: Incidentally, I'm experimenting with the RSS feed view of my tasks in Google Reader. I think I'll figure out a good use for this feature.