It doesn't matter if we can't see the difference between 90 and 120 fps, it is still nice to know you can hit 120, it is good psychologically. Personally, I'd rather it be unlimited, but I'm not sure how fps limits work in the UT3 engine.
What is the point in NOT raising it anyways? A dev has to take a second of his time to change one line of a cfg? I fail to see why we shouldn't raise it.