Lukaku is a very good player, and considering his age, the goal scoring numbers are impressive. He's easily worth 75m in this market, and I'm surprised Everton didn't hold out for more.
I don't think he's *that* similar to Drogba though, so it remains to be seen how well he fits in Mourinho's system. Drogba was a tough, physical bastard who reveled in making life miserable for defenders. Lukaku has the size, but I'm not sure he has Drogba's tenacity quite yet. He'll get goals either way, but will he make their attack better overall? Who knows.