Buddy passes (D-3 passes) can be a great thing to have, if you're flexible. There's never a guarantee of getting on board, since cancellations and such can make even the emptiest flights full, but if you are flexible you can usually make them work. Some destinations are nearly impossible at times, and AA actually issues a D-3 embargo every summer prohibiting buddy pass travel to Hawaii or Europe.

While it's true that you have just about the lowest priority of all the people on the standby list (you would be above 2 groups... D-3 travelers who checked in after you and pilots of other airlines attempting to jumpseat), that doesn't necessarily mean that you will be in a middle seat, or even in coach. I'm sure we've all been on flights that have departed with emoty seats in F and J. I travelled with a friend who was flying D-3 last weekend, and not only did she clear to first, we even got seats next to each other.

Speaking specifically to AA's pass program, D-3 travels pay the same charge for F, J, and Y on domestic flights other than JFK-LAX/SFO, while you have to pay for upgrades on International Flagship Service flights and the LAX/SFO-JFK transcons. While your friend can provide you exact pass charges, I can tell you that you will pay the same for any single flight between a US gateway and Europe or South America, and a higher flat charge for any segment to/from Tokyo; that is, IFS flights are charged flat fees, rather than by milage. AA charges D-3 travelers (as well as D-2 travelers) on a per-segment basis, so LAX-DFW-MIA would cost more than LAX-MIA nonstop, for example.