This week's book giveaway is in the OCPJP forum. We're giving away four copies of OCA/OCP Java SE 7 Programmer I & II Study Guide and have Kathy Sierra & Bert Bates on-line! See this thread for details.
A comfort level with Java is important to get the most out of Android -- absolutely.
Android is the kind of operating system you would design if you had the choice yourself. It is largely open and very extensible. It is available in all shapes and sizes and will continue to find its way into devices beyond mobile phones.