Per everyone else's messages, yes, you get priority check-in, security, boarding, seating and stand-by, plus lounge and luggage perks.

Anecdotally, having done about 50 US domestic flights with AA in the last year as a GCH, I have asked for upgrades every time (at check-in, gate or lounge), and generally been told they can put me on the waitlist but I will clear only after every AA pax with status (including their lowly Bronze equivalent).

This happened a few times, but was just as likely to be because they liked my accent as liked my status.

The only exceptions, bizarrely, were when I redeemed Avios to book my flights, when I was upgraded every time I asked, once without even being waitlisted and the others I was given equal priority to AA EXP. No idea why this was.

Also worth noting that this is a fantastic use of Avios, especially for one-way flights under a week's notice - cheap redemption rates and minimal taxes and fees, almost always Y availability.

Hope that helps...

MF