Yeah, an absolute must have if you need a real keyboard on your android device. I had been looking for such a keyboard for a long time since I bought my phone. And I tried several of them but none comes closer to Hacker's Keyboard.
Some other keyboards have additional keys like Alt, Tab or Esc but they do not work very well. They are useless, so to speak. This one has them all, function keys and even Pgup and Pgdn. Now I simply can't imagine using my android devices without it. Thank you guys.
Their website is here