Its quite clear that we would rather have a player in the Schneiderlin or Martinez mold, but it isn't going to happen this season, unless we pay over the expected market value for said players, which is something we don't do in principle.
Khedira doesn't play like a defensive midfielder at Madrid, but if you look at his stats from the 2012/2013 season he makes tackles, intercepts, and wins aerial duels more often than not. The major issue with Flamini and Arteta is the defensive errors they make (Arteta in particular), and lack of a physical presence (Arteta loses more aerial duels than he wins). Some of you are making it out as if he will give no protection to the back four whatsoever?
I expect him to be an upgrade on Flamteta, which he will be. I think Wenger understands that its a running game now, so a Khedira-Ramsey double pivot would be great. A lot of people underestimate Ramsey's defensive contributions, forgetting that, when fit, he's one of the best defenders in the team...