Status of the gmap "marker manager(s)" and alternatives

Hi,

I've searched quite deeply the Drupal site (and other resources) and as far as I could tell, the gmap module's "marker manager" is not ready yet. It worked in v4.7 sites but not in v5.x .
Is that so? If I'm correct, what's my options for a scenario in which I have a site with a map with over 30,000 entries in it (across whole US, for example).
I thought about auto-zooming to the visitors general area and thus saving him from the dreaded view of a too-overcrowded map... :-) . Yet, for this I need to map his IP address to his location, in an accuracy level higher than mapping his IP to the country he's coming from (like what is being provided by the IP to Country module). I've yet to realize how to achieve this.
The other option is the marker manager (Google doc on it), which is INOP, AFAIK (See this, this and that links for issues on this problem).

Thanks in advance!
Boaz.