I’ve been on a few - AF YUL-CDG in 2003, LY JFK-TLV (round trip) in 2008, and DL DTW-ATL (round trip) in 2016 (that one was a splurge since it was our last flight before their retirement - rode in 1A/K outbound, and on the upper deck returning).
I’ll miss them. Kind of a bummer not too many airlines ordered the 747-8.