The Linux kernel is very well tested over the years. In android, this has been slightly modified to suit the embedded / mobile environment. Linux as a OS is the most stable. So having the same as a mobile OS is also good.
For the developers the Java platform is most suitable for developing applications, since you don't have to worry about pointer and OO language increases the usability and maintainability of the system. Java forms one of the largest developer communities. So this combination is ideally suited for a mobile platform. Since java runs very slowly on a mobile, the virtual machine is modified. The Dalvik virtual machine is register based instead of the usual stack based VM's. This supposedly runs much faster.
Overall the platform looks very well organised and suits the mobile environment. Now after making this a open source we need to see the role of google in promoting and maintaining this platform.