For speed, nothing beats Genymotion. If also want to test the latest android, I found installing the latest Android-x86 image under virtualbox to be painless. If you want to run ARM code, be sure to install the Intel ARM translator. There are also several very fast Windows options too, such as Windroy[2], YouWave[3], and BlueStacks[4]. All of these solutions run faster than the official android emulator.