Since markers have been rendered with canvas elements, an ugly side affect has appeared.
When zooming out, the marker is scaled before the map (can be seen in Firefox).
This gives a very large marker before it is re-sized to normal after the underlying map tiles have been rendered.
Two group questions raised this issue :
http://groups.google.com/group/google-maps-js-api-v3/browse_thread/thread/eb1d9708641e8f94#
http://www.google.com/url?sa=D&q=http://groups.google.com/group/google-maps-js-api-v3/browse_thread/thread/d216f98b7bddaed2#

As per the second question, is it possible to disable the marker layer scaling during map zooming ?
Is it possible to have a single entry point to hide/display all markers ?

This would be particularly useful for those using clustering techniques.