When I bought my ticket I was told the boat would arrive around 3 pm (it leaves PP @ noon). Ha! 5pm ish is more like it. You will then be landed at a restaurant that offers to sell you bus tickets (at a premium). What really peeved me was their claim that the bus will drop you at "your hotel". Sure they do... Bollox, the minibus you'll eventually end up in stops at a bus station on the outskirts of HCMC and that's it. Btw, from Chau Doc to HCMC it was another 6 hours on bad roads moving at the speed of a motorbike.
Maybe someone can post about the slow boat journey?