Lady M asked, and I answer here.
What big bet did I win? Snape!
Dumbledore trusted him - a huge endorsement, even if she carefully laid the red herring of his mistakes.
I deeply adore stories that have bad guys redeeming themselves...or doing the right thing silently and invisibly, therefore not for kudos or to gain popularity. Snape's toxic ways are not excused by his redemption; just the opposite. He doesn't have a heart of gold. He has a black, flabby, coal-miner's-lung of a heart, broken early and often -- and kept on moving forward. He was wrecked in the womb. He had to die. His job was done, and he was free, the lucky dog. And for the good guys, who had no moral challenge -- only the effort to make (or die trying, which is the easy part)-- there was no loving Snape afterward. He had been too rotten. But now he has honor and great face forever. -- But then, I think Romeo and Juliet has a happy ending.