Yeah its kind of sketchy at times, dad and family all worked with GM and myself have been using the employee discount for 20 years, I have heard it all from dealers from they wont take it, to my dad who gives me the discount had to have had to buy a vehicle himself in the last year, to i have to trade in a vehicle to use it.
Truth is GM is kind of gray on this and really doesn't police it up. Other reality is some dealers just dont see it a lot and are ignorant. The other reality is dealers pretty much get MSRP from GM when the discount is used, its a little shy but not by much, so really is good deal to them and is a good business practice. But if they accept they can not get over MSRP. The other truth is the friends and family discount is only invoice minus 2% I believe where as the employee discount is invoice minus 8% I believe. In normal times you can usually negotiate a deal the same or better then the friends and family discount, and that discount is sort of garbage, but right now with no incentives or bargaining it is pretty good.
Most people need to realize there is not huge margins on new vehicles and your not going bargain thousands and thousands off beyond rebates and such. When coming to a number with a dealer and you are not using the GM discount, set aside incentives as GM typically reimburses the dealer for those. With that said the starting point for you the buyer is invoice and work down from there, invoice is not a good deal. Once you come to the lowest numbers you tack on incentives and rebates.