I'm in the same situation, taking a shuttle flight (LAS/DEN) next week for the first time as a 1K. Called the 1K reservations number today and was told the same as I've seen posted earlier here--1Ks can request complimentary upgrades on Shuttle flights by requesting them just like upgrades using 500 mile certs. They will clear (or waitlist) 100 hours in advance just like upgrades using 500 mile certs. Only difference is when you check in you don't have to surrender any certs.