Recently I took a train from Hanoi to Ninh Binh (soft seat) and later on soft sleeper from Hanoi to Lao Cai (Sapa). I enjoyed both trips. Apart from the trains being somewhat slow and in need of some cleaning and sprucing up a bit I found both the soft seats and the soft sleeper comfortable.
On the short daytime ride to Ninh Binh there were vendors coming through selling food and drinks every few minutes resulting in entertaining game of playing musical chairs with the passengers sitting in the plastic chairs in the isle.
On the overnight train to Lao Cai I believe there were snacks/ water sold at departure and coffee upon arrival. I took sleepers run by two different companies on my round trip but there was not much difference in cabin comfort and appearance.
I did not see any cockroaches or furry critters but after taking my glasses off, who knows.

On a side note I had no difficulty buying my ticket at Hanoi and Ninh Binh train stations. The staff in Ninh Binh even called my hotel on their cell phone for directions. The soft sleeper tickets to Lao Cai were bought at Hanoi Old Quarter from one of the many local travel agents.