You can tell they're having a lot of launch day backend pains. Push notifications are sometimes up to a day delayed. Follows don't stay followed, auto-follow on join doesn't seem to work at all. QTs don't show up properly half the time. Refreshing the feed takes forever, and you can tell when it fails to load your personalized feed, it just falls back on a generic feed with a bunch of random people. Even loading a profile page takes a noticeably long amount of time.