There is no strong separation between UI and server code which can lead to messy coding if you're not careful. It's just too tempting to use those hibernate beans directly as UI model. That's never a good idea.
I agree with your points, yet for some to a lesser degree. For example, yes, building the widgetset takes ages, but you can configure the build for a single browser in development, and then it becomes bearable again. Also, note that GWT has been replaced by HTML elements for newer versions.
I do believe Vaadin has its place, but as you mentioned, some cons prevent it from being used in some contexts.
As long as it works in your context, this is perfectly fine!
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