Hello people, what’s your opinion about using UI kits for serious project? I think that it might be usefull for inspiration, if anyone want to get here is list of some good(and free) UI kits http://graphicdesignjunction.com/2013/11/free-flat-ui-kits-for-web-mobile-ui-design/
I think it’s good for inspiration and if you’re not sure where to start. I personally wouldn’t use one because I usually make those things myself. But if I didn’t have those skills I could definitely see some merit to using it.
I think mostly using it for inspirations, for example when you see some cool color shade or anything else, you kinda put that into your elements, I think more using it for that then just puting already done elements into project.
There are times when I tackle something that I haven’t looked at for a while—for instance, a mobile project, after I’ve been immersed in designing web experiences—and a stencil or template like this might be good for reminding myself of the conventions and such for that medium. These things are constantly changing too; as Apple and Google refine and tweak and reinvent their respective views on how interacting with a mobile device should look and feel, so my own thinking and approaches to solving interaction problems evolves.
So yeah, they can be useful, for inspiration, for reminders and ideas. But it’s also too easy to throw a cookie cutter solution at a design problem because it’s there. And it may not be the best solution. As long as you’re wary of that, embrace templates, by all means. 
Exactly what @mattymcg said. I think they are great and all, and certainly the trend today is favorable to the flat UI. But as have seen, Google introduced material design which has added an evolutionary element to Flat. Things are not as flat as they seem, and we should encourage evolution for the sake of a better experience.