From what I read then it semed 10.5 Mail.app was following an unusual Tasks/Notes behaviors last seen in Claris Organizer (later Palm Desktop), and that Mail.app was becoming a PIM without a Calendar.
Which is kind of weird, but I figured it would all make sense when I got 10.5.
First, a digression.
Millions of people use OS X. Lots of well regarded bloggers write about OS X. So how come I'm the only one to get worked up over Apple's astoundingly screwed up approach to Tasks? I mean, I Google to see if anyone else has noticed the problem and I come up with my own comments from before I had 10.5?!
Shades of the Truman Show.
Ok, back to the post.
I think there are still a few deluded people who think Apple is uniformly excellent.
I can cure them of that. Try this experiment with the very latest version of OS X 10.5.5.
- Create a task A in Mail.app. Notice that you cannot add a Note to it. Your "task" is a one liner.
- Create a note B in Mail.app. Notice that you can "promote" it to a Task ("C"). You will now have a Task C with a Note B 
- Switch to iCal.app. Look at Task C from Step 2. It doesn't have a Note in iCal. Add a note "D" in iCal to Task C.
- Switch back to Mail.app. You will see Task C with Note B, but you will not see Note D. If you hold your mouse over the task long enough you'll see a read-only view of the iCal Note.
- Paste plain text into a Mail.app Note. Observe the formatting -- particularly the multiple lines between paragraphs.
I can't recall a comparable design screw-up in 20 years of lots of OSs and platforms.
So how did Apple botch this so badly, and how is this connected to the curious absence of tasks on the iPhone?
Here's my best guess. I don't usually pin Apple's glories or sins on Steve Jobs, but I'll make an exception this time. This has to be his fault.
This smells like a nasty collision between two powerful design teams, neither willing to compromise. When Jobs cares about something, he does seem to resolve these collisions. Obviously he didn't.
Jobs loves the iPhone. It has no tasks. That's another clue.
My guess is that Steve Jobs hates Task lists. He probably has some sort of trick memory and doesn't need them. Maybe it's his rebellion against the left brained world.
We aren't going to see Apple Tasks on the iPhone, or Tasks working on the desktop, until Jobs moves on from Apple.
In the meantime, I suggest
- Pretend Mail.app does not have tasks.
- Do not use the Mail.app feature that allows one to create a task linked to an email
- Do not create a task from a note in Mail.app
- Do feel free to use Notes in Mail.app if you can imagine any use to them.
Currently Mail and iCal both have a form of "Task" or "To Do" item, but they have different behaviors and Task notes are not shared. So a Task Note created in Mail cannot be read in iCal and vice-versa.PS. You can't delete Mail.app tasks, you can only complete them. Sigh.
This is not what we expect from Apple. It is embarrassing.
Please integrate Tasks between iCal and Mail. Tasks should have identical attributes, features and Notes in both applications, and should sync with MobileMe and the iPhone.
Update: I found someone else who thinks Apple's implementation is cracked, but I don't think he got as far as sorting out the whacky Notes behavior.