According to USGBC, technically you're not supposed to use the abbreviation LEED GA, they actually want you to spell it out. My belief is that it sounds too much like LEED AP which means a lot more, the green associate is the halfway license like the EIT. I have not placed it after my name.
My opinion. No, it's not worth it, unless you can double the CEU's up with another license it'll cost you money and I don't believe it's helped my career, LEED is not really about saving energy (more of what I do) they have a lot of things in there like installing bike racks, location of sites, permeable parking lots, etc. that you can get points for.
I have the PE, CEM, and Leed Green Assoc. The CEM was free, back when the stimulus dollars were available my state allowed all professionals in the energy field to take the class and get the certification free of charge, if you can get your company to pay for the CEM it's worth it imho, not because of the value it adds on your resume but the education in fields that are not your own, they teach you all about electrical, mechanical, HVAC, and building systems and give you a basic understanding of each system. The CEM is more engineering related while the LEED is more architectural.
In terms of difficulty the LEED was by far the easiest to get, followed by the CEM which was challenging, then the PE was the hardest of course.