On paper, Granit Xhaka would be a huge improvement.
From talking to friends on Wearside, they've been linked with dozens of players, which most are finding quite exciting. I think if my team had been singing largely EFL free transfers for several years I'd be bowled over by a link to someone like Xhaka.
I'm curious to see who else they add to the team. Right now it seems short of experienced heads, but I try not to judge these things until after the window is shut.