This also happens to me when trying to run a full-spec device. I lower the specs and resolution quite a bit since I don't even have enough memory to allocate for a 1GB ram virtual device.
The first boot will take some time. You can configure your emulator to use snapshots which will speed up the boot time considerably. Look into running the x86 image which will increase the performance of your emulator. Keep in mind if you have any armeabi-targeted binaries, they will not work (not an issue for most people).