Well, against common advice, I have 2 major projects planned for Construct and I'd rather get started with them now while I'm excited instead of wait a few months/years and lose steam. Also, most game design components can't be done without a bit of programming first and the art sometimes can't be done without the engine and so, yeah.
If possible, I want to build up the engine first; everything else can be done outside Construct. Which components of Construct are particularly buggy and/or prone to change? Are there any behaviours, objects, effects, or features I should avoid?