I used to work at FB, and while sapling is quite nice to use in practice, without the internal version of Phabricator to do code review (and, in all likelihood, mononoke), I don't think I'd pick it up again.
I've noticed that the system seems to repeatedly throttle me where it never did before. Logging in often results in being given an error until I try it enough times.
Sometimes attempting to pull recent changes from a repo will fail, and tell me that I pulled the recent changes even though I am stuck on an old commit. I tried several things to fix this and the only thing that seems to work is doing a hard reset on the latest commit id. I never noticed github doing this before.
I agree with you on the token system. It was a pain to figure out.
I've actually run into issues with throttling and stale fetches before, but it was due to a company proxy intercepting all requests. So effectively our entire org was hitting GitHub through a small number of proxy gateway IPs. Happened with AWS APIs too -- major throttling issues with terraform that seemed to be triggered based on the shared IPs.
Might be a longshot, but I'd check to make sure you aren't going through some proxy or VPN because I don't think your experience is typical.