Hello Fruity. Nice name ^^
I dont think its up to us if we can judge if we have progressed spiritually. I haven't got the gian to judge, where I am. Only Waheguru truly knows that. I think all I know for sure, spiritual progression is not as linear as saying, learn gurmukhi and you have progressed. Even by me saying the word "progressed" makes it look like, spirituallity is linear. But its not. A Gursikh friend told me about a discussion he had with a English guy in a bar. The guy had a cigarette in one hand and a pint of bitter in the other. But the stuff he was talking about was as if he had samadhi. One explanation can be that he did alot of bhagati in a previous incarnation. But I cant judge.
In my life, I was lucky enough to find Gurbani. I can't read gurmukhi and read my bani's in romanised text. One thing I have found is that, the meaning is slow seaping through. Before it used to feel totally alien, but now somehow, its starting to make sense. Even though I do not understand most of it, I recieve something extremely fulfilling by reciting Gurbani. I am not quite sure what it is. But it is something. One explanation I have heard is that there is something in the makeup of the sound current of Gurbani. Traditional wisdom suggests maybe it has a affect on the throat chakra, but I think its alot more than that.
In my opinion, learning Gurmukhi can only be a very good thing, but I dont think "spiritual development" is constrained to it. Is understanding Gurbani the important thing? Or is how we live our lifes according to that understanding the most important thing?