Perhaps the most significant feature of Google's Android open source handset software is the way they've finessed the Java problem. So far, Sun has totally controlled the Java ME code base. Yes, they've offered Java source code under the GPL, but not the complete source code for Java ME. Instead they offer PhoneME as an open source subset, ostensibly because Java ME incorporates components which Sun cannot provide under GPL. Then there's the question of the rate at which the Java Community Process advances...
Google has bypassed all this by releasing the Google-created Dalvik Virtual Machine under the Apache license. From ONLamp:
The development process is a standard one for Java developers: Java code is compiled into .JAR and .CLASS files. Google built a custom virtual machine to run these programs; it is called DALVIK (after one engineer's favorite location in Iceland.) The DALVIK VM is designed especially for Android to run on embedded systems and work well in low power situations; it's also tuned to the CPU attributes. The DALVIK VM creates a special file format (.DEX) that is created through build time post processing. The DEX files can be downloaded onto the mobile handsets and run.
Talk about energizing the Java community. This one component may have more impact than anything else in the Android stack.
UPDATE (20 minutes later): I just found this by Stefano Mazzocchi which describes Dalvik in more detail and, talk about energizing the developer community, just look at his last paragraph!