Thanks for posting that link, it has raised my Pandora excitment levels right up again after a bit of a barren patch this last week! The smoothing function is exactly the sort of thing I'd been hoping be able to use on Pandora, and Spiro looks pretty good too!
I think you'll always like the Vector drawing package you learned to use first the most, and for me that was CorelDRAW. I use Illustrator much more these days (mainly as it produces files that actually work properly when you send them off to a commercial printer!), but often find myself wondering why some things are much more complex and fiddly than they are in Corel. I also really like drawing in Flash, the way it smooths out lines as you're drawing makes drawing a lot of fun (if you're into that sort of thing). Inkscape looks like it combines the bézier tools I like from Corel with the smoothing tools I like from Flash! I would download it right now and play with it all night if I didn't have to go to work tomorrow.
I also noticed with great interest that the Screencasters demo was captured in a 900x650 sized window (not a million miles away from Pandora's resolution), and the guy didn't really use the full screen area to work in. If this all runs on Pandora at a usable speed, it really is going to be the best thing ever!