@Wainan: "If I want to know what a clump of units is then I'll zoom in, regardless of what icons I'm using." - that habit alone will stop you improving. 100% guaranteed.
"How do you remember how long it's been since you asked for the upgrade , taking into account any stalls along the way? As well as doing all the other things you need to do to manage your army?" - the point is to get a feeling for the eco, its (at some point) easy to tell just from the way your mass income behaves how your upgrades/eco is progressing. There is no strict formula (except if your senton air slot or something) when to upgrade/how to spend your stuff - you must develop a sense on how much you can afford, how long it takes, what the impact is like after some minutes. Anything that hinders this is bad for improvement. Imagine learning chess and using an opening book to look up all the moves every game - you will grow dependent on it and wont commit the moves to memory properly because you arent forced to.
@Box: While this is better than the original mod, the mex icons are, as Ftx also said, still horrendously bad. There is zero point to highlight mexes that much, because they always are in the same position (due to no random map gen unexplored games). Just stops you from seeing whats close to them -> bad. As I said already, stuff like SML/SMD highlighted is acceptable but any common structure should not have some bizarre icon priority like this.