Leaflet author here. The vectors should redraw properly. The quote by @nathansnider is referring to the fact that vectors are not reprojected, but they animate with a CSS transform during animation. If they don't redraw, you should set up a JSFiddle test case and file an issue on GitHub.
update: they currently redraw, but are not reprojected until the animation is over as of beta 2. We want to change it so that vectors are reprojected at least per round zoom, or once per a certain interval of time (e.g. 200ms), which should be a good compromise between performance and visual appearance.