Hi,
I've been using Inkscape to trace bitmaps and noticed that performance is somewhat erratic when working with a path containing thousands of nodes. When initially selecting the path with the node editing tool it draws all the nodes with their appropriate little icon, this takes an age. The other time seems to be when you select a large number of nodes, it draws all the nodes in their selected colour. When I zoom or otherwise force a redraw performance is much better.
I'm not sure how the code is structured, but it seems to be optimized for small numbers of nodes being worked with at one time. Would it be possible to only redraw individual node icons when this will take less time than it would take to redraw the whole window. Of course, knowing apriori which is going to be quicker is difficult so maybe a simple test of (say) 100 nodes changing state.