Easily one of the best shooters ever made. The atmosphere will always stay with me. That haunting soundtrack with great ambient sound and huge, empty, hollowed out areas that felt completely impossible to break out of just worked so brilliantly.
I dunno if it's aged completely well (I believe once the guards see you out of cover, everyone knows exactly where you are), but man, what an amazing experience.
It's funny you'd consider this "not aging well" since Watch_Dogs is horrible about that.