Genymotion is a quite new addition to Android emulators family. I got it recommended first by a tester working for one of the biggest Android development companies in Czech Republic and therefore I put it on my to-try list. After that I did not really try it, because I managed to get good enough performace on my desktop PC with Intel HAXM driver. But when I tried the same on my older laptop, I couldn't get enough performance to at least unlock the screen without lagging.
For some time I was using Bluestacks but it is lagging as well a bit and it is Android 2.3. So I gave Genymotion a try. It is awesome.

Development, debugging

Genymotion runs as a virtual machine in Oracle Virtual Box. The installer comes with Virtual Box bundled, so you don't have to worry about it. It also has Eclipse and IntelliJ Idea plugins, but I am fine using it standalone with adb. Deploy and debugging work perfectly.

Features

Genymotion is ideal for game development. It uses your hardware to run OpenGL, so it's fast - even on my old laptop. It allows you to select all the popular resolutions along with DPI - therefore it's very easy to test how ads like AdMob ads will look on screen in your game. Thanks to this, I have discovered that some small screens with very popular resolutions actually look quite bad in my game, Mr. Dandelion's Adventures. They cover important elements on the screen.

Available images

Also you have many options of Android devices to choose from - they get downloaded on-demand. I was very happy to see Android 4.3, but a bit dissapointed to find out that they do not have Android 2.3 yet. But according to their Twitter they are working on it.

Conclusion

When Genymotion releases Android 2.3 image, I will uninstall BlueStacks and never run the original emulator again!