Damiao is widely regarded as the best striker (finisher, as Matri) here in Brazil right now. He's the N.1 in the National Team. But we have to consider that Brazil is going through a big talent drought right now, Neymar apart.
He is not brillant, but he's got good physical qualities and skills. He's pretty quick for a finisher; he's got good movement off the ball, finishes very well with both legs, good on headers, is a very constant player... but not the smartest one. He's still 23 I guess.
Summing it up, I don't think he'll ever be world class. But at the same time, he has a game suited for Europe. I'm pretty positive he'll do well in Italy. He's way better than Matri IMO. He could become an important striker in Europe, 1 level under world class. Someone like Falcao, maybe.
Unfortunately, Internacional is a wealthy club and they will demand a lot of money. Loan is not an option for them. His real price is around 15/20M.
To pay more than 25 for him is not worthy IMO.
40M is ridiculous