From a Rangers fans perspective, you'd be gaining a player with undoubted quality. A master at reading a game and being able to break up play and also get the team on the front foot with penetrative passes. He's not really a goal threat these days but contributes well in building attacks.
With that being said... I was very critical of him at the start of the season. His form wasn't where it needed to be, however that could've been said for much of the team. He was then out the team for quite a bit but since coming back in has contributed well.
It doesn't look obvious that he has lost too much in terms of fitness as he gets older, but having only played in 31 of our games this season that may be an indicator that he is beginning to decline.