While working on a sample program that used xdpgeneric to encapsulate and XDP_PASS packets to the linux networking stack I discovered a regression in XDP and had a grand old time time reporting it to the xdp-newbies mailing list.
You can read my initial report on the xdp-newbies mailing list, and the resulting patch on netdev.
I learned two things from this experience:
xdp-newbies is a super-friendly place
perf is awesome
I am attending netdev 0x14 in March and am very much so looking forward to learning much more about this and more.