Anyone who doesn't think that Bale would be a good investment is pretty stupid.
Pros:
-Fast (we only have Clichy and Sinclair who are fast)
-A very good dribbler
-His shooting is fantastic from close range or short range
-His free kicks and corners are brilliant
-He's a winger (obviously) which is something we're lacking this season
-He'll turn Dzeko into a 20+ goal a season striker.
-He'll also create more goals for Kun
-Pretty versatile, can play left back, left wing or just in behind a main striker
-Young, still has 5 or 6 years until he reaches his peak
Cons:
-Expensive
-Diver (something we don't really want associated with Manchester City)
I think that Mancini should take a very strong stance with Bale and his diving.
If he dives, he gets fined or doesn't play next game (or maybe something not quite so extreme). But his talent is obvious, the guy is world class, or at least on his way to being world class. His value is only going to go up over the next few years.