He's a cracking player and I reckon that Bundesliga experience has prepared him for this season
He'll be really good for them and will ensure their midfield is strong enough to stay up
It's cracking business on their part
In all honesty, the reason he's coming to Swansea is because at Bayern he did not play regularly. From October onwards he was often a sub.
Don't get me wrong, it's a coup on their behalf and he is a good player but I think you're overstating the influence he will probably have early on.
He is, in my humble opinion, not the finished article yet and playing in a physical league for a lacklustre team will be a steep learning curve.