Tried a couple of googlemaps and OSM plugins and as far as I have seen, this is the best and easiest way to put up maps and markers on a wordpress site.
You can choose to display various google maps (satellite, road, relief, …) or open street maps which is neat.
The overall interface is very professional and there are lot of usefull options.
the best part: it’s easy to add and manage markers even for non-technical persons.
As someone suggested: I would love if users could add and manage their own markers.
It’s irrelevant to the plugin itself, but I also appreciated the way the author ask for support in a non intrusive way and offer different options to support him (paypal, amazon wishlist, buy though his amazon affiliate store which cost nothing to the user, as well as flattr).
Planning to use of one of these option very soon.