After nearly a year with two mapping platforms running in parallel, Google announced today that Google Maps V3 had graduated from Google Code Labs to become the primary maps API. Previously the newer version was recommended for mobile applications, the original reason behind the Platform rewrite. With V3's graduation, V2 becomes deprecated, but will continue to work for now.
Google has added new takes on V2 services to the V3 API, such as driving directions in November. Recently, new features, like elevation data, have come to only V3, which prompted us to write that Google "could either be signaling that V3 is the way forward or that elevation data is of more use to users on the go." The trend continued with Google adding a bicycling layer only to V3.
Along with V3's graduation comes another feature from V2: StreetView, the 360 degree photos available in many cities. Instead of using a Flash player, the V3 implementation uses standard HTML. Google said the reason for the move away from Flash is to support devices like the iPhone.
It's been a good, long life for V2, which was released over four years ago. It's hard to believe now, but at the time it didn't even have a geocoder to convert addresses to coordinates. Still, during that period we saw most of the 1,964 map mashups built on Google Maps. It is perennially the most popular type of mashup.
If you're rewriting code to support V3, you might consider taking the opportunity to use Mapstraction, an open source Library that works with a dozen mapping APIs. We wrote about the Mapstraction sandbox a year ago. You can use Google Maps (V2 and V3) via Mapstraction and easily switch to other providers. It's a useful way to plan ahead, because who knows how different Google Maps V4 will be.