Great deal for the Angels. It seems like a ton of money (it is) and I'm sure it won't be a great contract when he is at the end of his career, but is was necessary and the first 5 years of that contract might be worth more than half of the monetary value anyway.
Will it burn them in 10 years? Possibly. But the next generation of guys that will be signing when his time is up are 13-15 years old now. So you can't worry that far into the future. Plus you can't put a price tag on having the best player in baseball on your team for the next 12 years.
I really hope they can put together pitching. #7 farm system in baseball, some of those guys are going to have to go for arms. Trout is Trout, Simmons is good, Upton, even Pujols isn't as bad as he is made out to be (because of his contract). They need arms and they need them badly. More than any other team in baseball probably.