very inspirational reading, Shishkovtsov is smart guy

http://www.eurogamer.net/articles/digitalfoundry-tech-interview-metro-2033

especially deferred reflections - so simple idea to make reflections in deferred shader! just render reflected attributes (position, normal etc) into Geometry buffer and draw as usual.

also I am thinking about implementation of Exponential Shadow Maps after reading it.

I read the article half of year ago and have rewritten engine significantly after that. Thread pool was added, engine was detached into several parts etc.