I will add some feedback as well.
I started with Vaadin 8 out of college with no full stack experience, just plain old Java.
I began by creating a CRUD example in Vaadin 8, as I was working my way up to a production webapp.
Then I moved onto Vaadin with spring, which I now use in most of my Vaadin apps, the documentation was great.
I moved to Vaadin flow as soon as it came out. Everything was different but after learning the new APIs and methods it was somehow simpler.
There are still some “features” I scratch my head at, it’s not perfect yet, but since I had no longterm experience with V8 I seem to like it a bit more.
My biggest issue is most of the good answers to problems are for V7 and V8 and can’t really be implemented the same way in V10.
Number Fields are an issue too. I don’t want formatting xxx,xxx and LongToStringConverters no longer work properly, whether or not its a number box or text box. Because of this I have had to my database to be a string datatype instead of a Long, as it should be.
For now my apps are simple and only do a few things. I like the direction Flow is heading, but as with any new framework/stack there will be hiccups.