The speed of development can be compared to Unity3D which was my previous choice for creating games with many characters or large worlds in it (as opposed to mostly AI).The fact I could use JS instead PHP gave me some peace of mind at first but then you realize how powerful Javascript really becomes when combined with other things like nodeJS etc..and this gives one even better results! There's not much i dislike about kiwijs so far just maybe its documentation needs work since there are too few resources available online regarding using javascript as backend coding language if your interested in working together with js. It comes integrated very well into NodeJs which helps solving performance issues while implementing server side code. Game logic implementation has become easier now than ever before due to the amount of tutorials out their explaining certain concepts from scratch step by step, making learning easy enough without having prior experience in such.