When you play your own game every day during development it's easy to get too close to it. When you're too close you can't see the obvious flaws that others with fresh eyes might spot as soon as they sit down to play. It takes a real effort to step back and look at your own game with fresh eyes, and sometimes it's still not enough.
"Kleenex Testing" is an extremely useful form of testing that can help you see the forest for the trees. We call it Kleenex (or "Tissue" if you're not familiar with the Kleenex brand of tissues) because you use it once and throw it away. We bring the fresh eyes in to play our game for truly the first time, analyze the results, and then do not use that same tester again for the same purpose.
We recently did such a test and the first thing that became apparent is the controller layout that we had always felt was just "ok", but had become accustomed to, was going to be inadequate and was in dire need of an overhaul. Fortunately we're still in our prototyping phase so such changes are very easy and inexpensive to make. The controller layout was overhauled last night and we're getting ready to playtest with the new configuration now!