Here's the end product - what I really wanted to do was put up a homescreen of notes - where I could see them all at a glance. Or at least more than the one allowed here:
Tapping the note does bring up a page of four Post It-style notes, though you have to use the push pin icons to select which of the notes is to be displayed at any one time on the homescreen:
Note that, unlike Slippy Notes, you can enter more than one line of text per note, i.e. you can use carriage returns, which is slightly more helpful.
Also rather neat is that two other styles of note are available. Here's one based on torn out pages of a paper notebook, for example:
Could it be that only be allowed one instance of the widget for each of these applications is a platform limitation? Comments welcome if you can clarify the situation!
Unlike Slippy Notes, which is commercial, Notes Wall is free in the Nokia Store.