Just committed:
* Interruptible display: Previously, Inkscape could not do anything until it finishes the current screen redraw. Now the redraw is made interruptible, so that Inkscape responds to mouse and keyboard input and can abort the current redraw and start over if you do some screen-changing operation. As a result, Inkscape now feels much snappier and more interactive.
So, while redraw is not really any faster now, it _feels_ much faster, especially for things like zooming, scrolling, etc. Enjoy.
I fixed a couple bugs that were exposed by this change, but there may be more. In particular I suspect there might be a crash when you quit Inkscape while it's redrawing. I got this crash a couple times but it's very hard to nail it down. If you can cause it reproducibly please let me know. Other than that, it's working perfectly for me in the last few days.
Thanks to Mental who suggested this change :)