your benefits include :
- free access to preferred seating
- check-in at J class
- extra baggage allowance / priority tag on luggage
- lounge access (keep in mind that AF lounge at LAX is one of the worst in the network...it's the ex-NW lounge)
- priority boarding
- you may have a kind of priority in case of op-ups but many other parameters seem to count like the fare you paid, your "attention score", etc. Op-ups will occur only if your original class of booking is oversold. You can use miles for upgrade if your booking fare is among the most expensive (fully flexible and refundable fares).
- 100% extra miles earned