Running a real ARM emulator is still slow but for most things running an intel emulator with haxm will be fine. An actual device will be faster but the emulator will be suitable for simple test

You can use Genymotion is which pretty quick even on my Macbook Pro 2011 machine.

Edit: Looks like it's not longer free.

The Intel emulators these days are very fast, especially the ones you can create in Android Studio 2.0+. They are still resource hungry (RAM mostly) but they are now faster than developing on a physical device.

In Studio 2.0 it got much better. Just make sure you're using a recent gradle version in your project config (it'll prompt you if you open up an old project).

Haven't had to use Genymotion since 2.0. Instant run is getting better w every release, I surprised the iOS dev last time I showed it to him.

Yes, use an Atom based image versus an Arm one, and it should be much faster.