If no one's said it yet, I thinking getting Construct to work with general PC controllers, not just the 360 control type, is a must. If you want this to go bigger and more public with a solid release, people are going to be expecting being able to use their generic PC controllers.
If I'm not mistaken, there's two control types, right? XBox 360 has its own type, so it's good that got out of the way, and then there's a universal type for all the rest? 360, and PC? I can't remember what the non-360 control type is called though...
But seriously, if anything, getting Construct to work with general PC controllers should be a top priority for 1.0.