Benefits I've used so far:
-Priority GS phone line
-Booked a saver business award based on IN/R class availability.
-Booked a saver coach award based on T class availability.
-2/2 comp domestic upgrade cleared on award ticket with companion based on PN class availability.
-Airport checkin agent proactively bumped another party out of their seat so that I would be seated next to my companion
-GS checkin line with agents on hand to bring your luggage to TSA screening at airports where you normally have to.
-Boarded before Group 1.
-Global services email address for prompt email service.
Benefits I haven't used yet:
-GS line can call the airport to have PR-1 status added to plan B awards
-Upgrade based on P class availability within 24 hours of a flight
-Mercedes transfer for close connections at DEN/EWR/IAD/IAH/LAX/ORD/SFO (haven't connected yet)
-Refund revenue tickets (Case by case basis, but seemingly most agents will)
-Book a saver award for a companion in business or first regardless of available award space if GS member is on a revenue ticket.
-Use a GPU to upgrade a coach award to business based on PN space.
-Use a GPU to upgrade a business award to first based on ON space.
-Access a Global First lounge when flying in business in IAD/HKG/LHR/NRT/ORD/SFO.
-Access a Lufthansa first class lounge when flying United first in FRA or MUC.
-Private GS checkin/front of security line (EWR/IAH/ORD/SFO, soon LAX)
-First meal choice
-Transportation to a paid hotel room in case of overnight missed connection regardless of cause.
-Confirmed seat on the next available flight in case of irr-ops, even if it's overbooked.
-Upgrade a companion in coach to business if GS member is in a paid business seat, regardless of space.
-Access to arrival lounges in FRA (LH), LHR (UA), and ZRH (LX), regardless of class of service.
-Soft landing from GS to 1K if you don't re-qualify for GS.
Any other benefits I'm missing?