Nice work!

Regarding sync speed: Bear in mind the python server implementation has a per address throtteling in place to avoid DoS. One of the shortcomings of the current python implementation is that one client with lots of addresses can hog server ressources to a point where all other clients are hanging in "sync" until the large request with lots of addresses is served. To avoid ressource hogging by one client throtteling per address was implemented and works rather well as a workaround.

[Edit: spelling]