Yeah migrations are the biggest issue for me. I really don't like not knowing what the actual shape of the document will be. Missing transactions, and not great relationship performance makes modelling some systems more hassle than it's worth.

I gave it a good go to use mongo and firestore for a few projects, but after a year or two of experimenting I'll be sticking to SQL based DBs unless there are super clear and obvious benefits to using a document based model.