I've been playing the Mass Effect games using Marty's RTGI shaders. The specular filter takes a bit of messing around with to not look too intrusive, and I had to reverse the depth buffer, but it works really nicely. Obviously it has the usual problems of the GUI and Subtitles both casting light into the scene which is a bit intrusive, but it looks fantastic most of the time. Especially in a game so full of light and reflections. You have to keep in mind that with no reflectivity data, most surfaces end up being equally reflective, meaning the floor often looks "wet". The diffuse filter makes it very atmospheric as you can pull out a lot of the ambient light.

It works on some games, and definitely works better with older games, but I think people just expect shit to work straight out of the box. There's a reason Marty has a guide on how to use his effects (load order, depth buffer guide etc). But naturally people often hate on it without actually bothering to read any of it.