I recently travelled overland from Zanzibar to Rwanda and found your Bradt guide invaluable. Bus from Dar to Dodoma then Mwanza, ferry to Bukoba, minibuses/taxis to Kigali.
For what it is worth, I offer the following updates.
Zanzibar, Pongwe: Seasons Lodge Hotel, next to Pongwe beach Hotel, new, opened a few months ago. Very good. Santa Maria Coral Reef appeared closed.
Mainland trains: Dar-es-Salaam to Dodoma not in service. Dodoma – Tabora (and beyond) OK, twice a week, Wednesday and Sunday. I witnessed the departure from Dodoma on Wednesday at 9.00 a.m. Tabora to Mwanza not in service (since about 2009).
Dodoma-Mwanza main road all tarred. Had one bus Dar-Dodoma (8 hrs) and another Dodoma-Mwanza (9 hrs)(it had started in Dar). Bukoba-Rusumo tarred except a 30-mile stretch north of Biharamulo (new road under construction).
Dodoma: CCT Hostel OK, single room now TZS 11’000.
Mwanza: New Pentagon Hotel OK; Deluxe Hotel now a brothel! New: upmarket Gold Crest Hotel opposite New Mwanza Hotel. Fourways Travel agency gave wrong information on ferry to Bukoba (wanted to sell us flights there instead!)
Mwanza-Bukoba ferry. “Victoria” goes twice a week. We left on a Thursday at 9.00 p.m, arr Bukoba 7.00 a.m. after short stop at Kemondo Bay Port. Second class cabin (6 bunks) TZS 23’000.