Hey,
I could not resist a temptation to do some optimisations and achieved about 10 times faster rendering in some situations (complex drawing zoomed to 1000-5000%). The idea of optimisation - eliminating nodes outside of rendered area, so no bezier calculations and other stuff is needed, so rendering of zoomed image consume less memory and is also faster. The question is - should I continue work on that (solve last minor issues) and try to commit it or I'm the only one who uses Inkscape with complex drawing and zooming in to the finest detail? The fix make code somethat less readable/maintainable, so there is a price for performance improvement. But if there will be support for such thing, I will try to finish it after Easter holidays and see how it works.
Andrius