They've followed through on their promises so far, and you can actually self-host pretty much the whole stack today:
https://alice.bsky.sh/post/3laega7icmi2q
I'd perfer for mastodon to take off personally, but really at this point both are good options and worlds better than twitter.
You can run your own relay, though:
https://whtwnd.com/bnewbold.net/entries/Notes%20on%20Running%20a%20Full-Network%20atproto%20Relay%20(July%202024)
I do prefer Activitypub overall, and it's certainly more mature, but any efforts towards decentralization should be encouraged/celebrated.