I've been playing with SPOffset today -- great stuff! It has some awesome potential as an artistic tool.
That said, there are a few issues that bug me:
1. something's going a bit wonky with the associated NRArenaItem -- an assertion keeps triggering about the object's bounding box. Unfortunately, until I figure out what NRArenaItem::state actually means, I'm not sure of the best way to fix this.
2. I think perhaps Inset/Outset should modify the original path, rather than making a duplicate. Its behavior of duplicating the path and leaving them both selected surprised and frustrated me.
3. I'm not sure the use of xlink:href is really SVG-compliant in this case ... also, the behavior of following the original path was also a little surprising and frustrating, once I managed to get the original path selected without selecting the outset.
-mental