I have been using Lit in production for 3 years now. I think it is the best abstraction over the web components API out there.
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I have actually wrote a few web components by hand in an environment where I didn't want any external dependencies and when that requirement was dropped I really liked how easy was to convert them to LitElement (and how much nicer it is to work with them).
I also have embraced the shadow DOM which is a default, but I think it's more trouble than it's worth. Now I use LitElement without shadow DOM and it works great as well.
It's trivially easy to create Lit components without shadow DOM so I don't really care and use both.