The guy is 27 years old and has consistently been one of the top 5 players in the PL for a good few years. Rooney has a great work ethic, plays with a lot of heart, runs more than most, has great versatility and is the complete striker. He scores with his right peg, his left peg, good in the air, poacher's goals, wonder strikes, freekicks, finesse goals - you name it. He also has great vision and is an excellent passer of the ball.
I don't particularly like the guy but - there aren't many attacking players out there better than him, especially if he is to be the focal point of an attacking unit. Signing Rooney would IMO be one of the least risky investments a club in England could make.