RE: long delay, no window on startup: will be made much better by the QT splash screens in bitcoin 0.5.
RE: lots of GUI bugs: whole rafts of wxwidgets-related bugs will go away with the switch to QT in bitcoin 0.5.
RE: incompatible on older version of windows: I don't know nuthin about windows compatibility, somebody want to volunteer to investigate? Is bitcoin 0.4 less compatible for some reason than 0.3.24 was? (shouldn't be...)