We actually did the reverse cruise from Phnom Phen to Saigon.
Though advertised as a 3 day 2 night cruise we spent less than 24 hours on the boat.
The boat was ok, the food excellent. The side trips average.
Just some advice, read between the lines. It's as advertised but we hadn't appreciated that we would spend 4 hours on the speed boat having spent 90 minutes waiting for the boat, trip was fine along the Mekong, but arrived in the dark with no-one to greet us, though hotel was next door. The Victoria, which was great.
Next day a three hour taxi to the boat, interesting travelling through the countryside and towns. Boat left about 12pm.
After the cruise we disembarked at 8am and had some trips. The Sampan ride was short and quiet a disappointment.
Three hour taxi to Saigon then, though a nice lunch stop was included.
Overall, we didn't think it was worth what we paid. And keep your cash close, we were 2million short when we checked our money later.