well, i've seen people using that lens before. In general, I guess it's all about what you wanna capture. Full body? Half body? I mainly use 24-85mm as well as 70-200 if the distance is too far. Gives a better bokeh as well.
I believe a 50 f1.8 is reasonable if you are not too near to the stage. Totally agree with the point as to what you intend to capture. Other than that, full body shots may not be very possible if you are too near though. Just my thoughts. (=