What's the history and status of ASPA? As far as I can see, it's a fairly active draft with the IETF: https://datatracker.ietf.org/doc/draft-ietf-sidrops-aspa-ver...

It says it's on the standards track, but it's clearly quite new. How well has it been proven out? This page from Hurricane Electric shows <3% adoption: https://bgp.he.net/report/rpki_and_aspa

It's still very early. RIPE and ARIN have only supported publishing them for a few months. ARIN made very little noise about it during the rollout, and many networks are probably still unaware. Give it a couple years, and I expect we'll see fairly good adoption among those already publishing ROAs. There will still be the never-RPKI holdouts, however.

HE publishes their full ASPA table here, if you're interested in digging in: https://routing.he.net/?cmd=display_aspa_table