The Google Maps Javascript API Version 2 has been officially deprecated as of May 19, 2010. The V2 API will continue to work as per our deprecation policy, but we encourage you to migrate your code to version 3 of the Maps Javascript API.

Google will issue an announcement if the current version of the Service will be deprecated. For a period of 3 years after an announcement (the “Deprecation Period”), Google will use commercially reasonable efforts to continue to operate the Deprecated Version of the Service and to respond to problems with the Deprecated Version of the Service deemed by Google in its discretion to be critical. During the Deprecation Period, no new features will be added to the Deprecated Version of the Service.

Google Maps v3 has bought about quite a few changes. One of the biggest notes for me was the lack of a v3 equivalent of GDownloadUrl(); a function previously included in v2 to make asynchronous calls to a script file. Google took a step in assuming that most people these days, in addition to their API, are using some form of Javascript library (Mootools, jQuery etc...) and now you need to form your own XMLHttpRequest be it with traditional Javascript or with a library wrapper function. In Mootools' case it's Request() class.

Another nice fall out of upgrading to v3 is the need, or rather lack of it, to specify an API key! With v2 I had to create multiple API keys for the production environment servers. With v3 this is no longer the case as API keys are no longer required. Nice!

I'll add more to this post as I find it.