From my initial tests, it's very clean MVC (a bit verbose). Also the deploy story is not too good... (frontend code ships as a .war). Does anyone have experience with this, good or bad?
UI5 obviously has the weight of SAP behind it (be that for good or bad!) and new releases seem pretty frequent. For developing web apps to consume SAP data at least it seems the obvious choice (it's very much geared towards consuming oData which SAP Gateway provides).
I'm also not a huge fan of enterprisey software development.. SAP and most Java projects make me pull my hair out just getting an environment for development setup.
Still OpenUI5 is just js files in the end, so hopefully entreprisey people can't mess it up too bad ;)