We're working on a consumer project at the moment that makes heavy use of mapping technologies. We built the project with google maps, but ran into a deal breaker where placemark links in parsed KML always open in a new browser window, rather than the same window that is sometimes preferable.
Google seem to have acknowledged this is an issue, but they acknowledged it 2 years ago and have done nothing since - presumably for their own good reason - however for someone developing tools against the API, it can be a real headache.
Enter the open source community and a great product by Lance Dyas called GeoXML which is a new parser you can use for KML files (and much more) within the Google Maps API. And the BEST feature ... well for us, it DOES allow you to open links in placemark info windows in the SAME browser window. Great!
Beware that sadly the project lacks any real documentation and getting started can be rather hard. The documentation for another project EGeoXML is a useful starting point.