The MapWindow Version 4.7 RC2 has now been released. This is a good sign and seems to indicate the time line for the final release (October 2009) will be attainable. I have notice some bugs have been fixed for this RC including cleaner install on Vista machines and some issues around cartographic elements like exporting the scale bar and north arrrow. A couple of bugs that are still to be resolved at this point are previous zoom issues and incorrect scale bar showing for printing and previewing maps.
All in all this release (4.7) promises to be a significant improvement on 4.5. There has also been significant movement on version 6.0 which is being developed in parallel with the current version. Visit http://www.mapwindow.org for more details.