So I tried to dig into UI5 and started to build an application from day one. The first steps were great. Since I was used to code everything on my own from scratch, this was exactly what I was doing here too. The big problems began, when I tried to display some data from an Odata-service in a list, make it clickable, navigate, select some items and call some more services. Basically, when I started a small, but real project with limited knowledge of the underlying concepts. It took me a lot of hours to get this small task to work the way everybody wanted it to be. Nevertheless, in the end it worked and everybody was happy.
Afterwards I took a step back and looked at my work. It was kind of ok, but not beautiful. That's when I started to learn it again from the beginning. I read a lot of blog posts here, tutorials and introduction in the concepts and the architecture of UI5 and Fiori. As you might have guessed, this opened my eyes. Once I learned how UI5 is intended to work, making any component run was way easier. To be honest, this turned my mind from "UI5 is ok" to "UI5 rocks and I don't want anything else". Everything I learned so far convinces me, that UI5 is the was to go and that there a many, many great ideas realized in a professional way.
I'm really looking forward to work more and more with UI5.