Kevin,
I reviewed your page at http://www.angelfire.com/mi/kevincharles/inkscape/ncwf.htm - thanks for the detailed description. I just committed a fix to Inkscape CVS. Now you can achieve your result with a single click. In Node tool, either Ctrl+click the node, or select it and click the "Make selected node smooth" button. The node will get handles and its adjacent segments will become curves, but the neighbouring nodes will remain cusp.
Woohoo! But since you started this, I have to comment... First off, I'm so glad that we're headed down this path with the node editing tool.
1) With Illustrator, when you pull the handles out of a node, it is symmetric until you release the mouse button. Basically, you pull the handle out of one side of the node and it automatically extends the other handle the same amount in the opposite direction (but once you release the button, the handles are free to move on their own). The thing that makes this handy is that you can control how far the handles extend from the node, instead of them just appearing at a set distance. The nodes are also basically cusp after that first mouse-up too... so you can move the node handles independently. I guess what makes it weird for me in our current implementation is that you ctrl+click, and they appear... instead of you pulling them out of the node and controlling all in one mousedown/click. Does that make sense?
2) Another benefit of node editing in Illustrator that may already be possible in Inkscape (although I don't know how), is independently getting rid of node handles. What I mean is that if you have handles pulled out of a node, you can snap 'em back into the node (so they don't extend from it at all). This is also very handy.
Hopefully my description makes sense... I figured I'd throw it out there since you were working on node editing.
-Josh