I got this too (for GLD). Ironically, I just signed up yesterday for the PLAT challenge which I should fulfill in the next month or so with planned travel. I also signed up for this since it comes with 10 upgrades which are valuable.
I just hope it does not cancel out my PLAT challenge! We'll see. I have confirmation of both so hoping it works OK. Says it takes 7-10 days to reflect changes in account. I welcome the GLD opportunity, although my upcoming travel is already booked in a premium cabin.
It works to AA's advantage as I am actually planning to shift my business from DL to AA this year. I am tired of DL's bad redemption rates (particularly for international flights). Since most of my travels require a connection anyway (either on DL or AA), and some are LAX-JFK, there isn't much difference in my preference otherwise.