For those starting out on EQ, I think spectrum analyzers can be used as a sort of "visual guide" when you are EQ-ing. For example, if you hear a very annoying overtone in an instrument that you want to EQ out but can't seem to really detect which frequency it is, you can fire up an analyzer, solo the instrument and look at where the peaks are. With a high enough FFT window size, you can get really fine resolution, and it helps in your surgical EQ-ing. Of course, some guys with a little more experience would be able to identify the freq range on listen, and use a sharp EQ boost to isolate the frequency. In this case, they do not need the analyzer at all.