I don't think anyone is actually jumping for joy in this scenario or trying to say that Caulker is the second coming of Christ.
We need depth in this position desperately and are reaching a crucial part of the season in three trophies and in the league where games are coming thick and fast (though he is cup-tied in the League Cup - think he is ok for the Europa as he only played qualifiers for Southampton)
He's easily available to get in for the run of games we have coming up- evidenced by the fact he joined today and can play vs Arsenal- done swiftly.
He's played in the Premier League so has some experience- well at Swansea, bad at QPR etc.
He's taller than Ilori, Enrique, Lucas and Can - so should help in and around the box for defensive set pieces.
On a personal level for him - he gets the chance to have minutes in the FA Cup and the Premier League - and show people he is deserving of a move from QPR back into the league next season - so the motivation should be there to put 100% in.
He ticks the limited boxes we need ticking at this very moment in time. Presumably at the end of the season he will go back to QPR and we will look for a more long term solution. I really don't know why anyone's reaction isn't 'Oh sweet, he might help us out a bit on a temporary basis in this shitstorm we find ourselves in'.
Weird, really. Oh well.