Bit in love, I think :). In a way, this feels too short for something that covers so many years, but that''s more of a nagging feeling than anything terribly serious. You've done this so elegantly that I don't feel anything other than satisfaction. I adore the language - the phrasing seems so appropriate. The backdrop of the building of the Bridge is a wonderful frame for the story, the monumental task, the father to son to adoptive-son legacy of it... love, love, love.
In all honesty, the Harry-is-gay subplot seems like a bit of a bone for the slashers (we must have our queer lads somehow ;) ), but it's a fine enough reason to get him out of the country and add in the bittersweet parting, and has the interesting issue of the then-illegality of male homosexuality.
I'm also rather thrilled to see a Snarry relationship that's something other than romantic. Which is not to say that I don't like it when they shag like bunnies :). But it's utterly delightful to see a different aspect of the Snape-and-Harry combination explored.