How good is Construct 3 for game development?

1. Yes. Especially for 2D-platformers, -tiled or -top-down games.
2. Event sheet coding comes with a solid tool-set and shouldn't be underestimated. It should allow you to achieve basically anything you can imagine in 2D, even without javascript.
3. Unfortunately CPU overheads for nested loops can become aparent. Depending on the size of your game, or the complexity of your systems, you may want to replace these loops with javascript.

I think there's not a single game out there yet showing the true potential of Construct 3. There are only a handful of hidden gems, that's because C3 is mainly pulling in less experienced game makers due to its event sheet premise.

So feel free to bring justice to C3.