I’m a bit late to post this but GreaseMonkey 0.5.1 is out, so no need to tinker with the beta any longer.

MyLocations still work fine. And you might want to check the cool Google Maps tools on Matt King’s GNIKville wiki. His gmap_extras is more flexible than MyLocations, since it requires no web server and save/delete of locations on the fly. I might modify it to add the drop-down menus from MyLocations to the “directions” form - at which point I should be able to drop MyLocations.