Limited playing time and being forced to play with less freedom at Barcelona MUST have made him more suited for a holding role.
If you look at the traits most people here look for in a midfield addition, Song actually possesses them:
Big - check
Strong - check
Good in the air - check
Dynamic - check
Strong in the tackle - check
Better than decent on the ball - check
I think most of us want a player who is more disciplined positionally than the Song we mostly saw here, but it isn't beyond the realms of possibility that he has actually improved that aspect of his game.
There is of course also the speculation as to WHY we let him go so easily without putting up much of a fight; if the rumors that he was disruptive are true, then there is of course no chance we are interested in taking him back. Personally, I'd be well pleased to have him back, and I reckon he can be had at a decent price too this summer. That is of course only of any value if we put what we 'save' from that into the 'Beast Striker Fund'.