The thing I miss in my current project for instance would be the fact that it's hard to be granular in queries, let's say we have a root that queries a set of products.
useQuery({ query: 'query { products { } }'})
We'd have to tailor the selectionSet of products for all the sub-components here. If we know we have a ProductList child, I'd love to make it look like this:
export const ProductList = function(){ return jsx }
ProductList.dataRequirements = ['fragment productListFields on Product { id title image}'];
This in turn could then make the root component a bit smarter and enrich the queried data.