As a former Palm OS user, too, I'm appalled at just how badly every other vendor has missed the mark on PIM, including the new Palm's Pre. My recommendations for calendar are to check out Jorte Calendar Widget and iRT Calendar. Neither are the equal of something like Datebk on P-OS, but they're both better than the stock app. I actually use both: iRT for calendar view, and I have iRT configured to go to Jorte when adding an event. Many like the Pure Calendar widget. I played with it only briefly, so maybe I missed functionality, but it didn't do it for me.
iRT is planning a new "Pro" release later this summer which sounds like it'll meet my calendaring needs, and Pimlico is supposed to be porting Pimical to Android, so I'm hoping the calendar issue will be solved soon.
I'm not a heavy user of tasks, so won't try to give advice there, but this one looks like it has promise:
http://forum.androidcentral.com/and...6-taskit-new-todo-project-management-app.html
Good luck.