Usage varies. For Add Note, of course you'd want to be in edit mode with onscreen keyboard invoked (for those with onscreen keyboards).
But when clicking on existing notes, I prefer to be in view mode (without onscreen keyboard invoked) as I'm much more likely to be retrieving info from existing notes rather than editing the note. And the keyboard annoyingly hides half the screen and forces an additional keystroke (back), which on my HTC Hero is a hardware switch. If editing is required, the keyboard appears with one touch on the highlighted text area or a separate edit icon.
Others might prefer to default to edit mode. I don't know. But I'd prefer a menu setting (as provided in AK Notepad). Check out the 3banana implementation also. It defaults to view mode but provides a pencil icon to invoke edit mode if required.
This may seem minor but it's the annoying little extra keystrokes, particularly when hardware switches are involved, which make one UI seem a lot slicker than another. This would be a huge improvement for my usage.