It says "Aplikacja która w przyszłości może będzie dobra, ale na razie jeszcze dużo jej brakuje."
Google translate told me that it's Polish and in English it means "Application that the future can be good, but for now its still a lot missing."
I guess this user must haven't seen the statement I put in the market: "This is an Early Access Preview version , so very premature yet."
The commenter left a rating of 2 stars which changed the 100% 5-star rating so far (5 ratings before this one)
Lesson learned: you can never go too far to manage user expectations.