He will be missed for stopping almost unstoppable goals and will not be missed for mucking with simple saves. Overall, I have mixed feelings, just like his performances.
I have mixed feelings too. I've always liked him, even back when he had his dodgy start to his United career. But if the opportunity is there to upgrade our first choice goalkeeper, we absolutely have to take it
Getting a keeper that could claim balls in the box and distribute the ball with his feet would make us a much better team. Think about how many goals we have conceded because we were caught in possession playing out of the back (which is often down to De Gea choosing the wrong outlet pass and leaving a player in a tough spot where they get closed down immediately).
And don't even get me started on set pieces, we have gotten killed on free kicks and corners for years because De Gea can't control the box and claim the ball.
But he's also had a great career with us, thankful to have been able to witness all the legendary, unbelievable saves that he's made over the years.