After years of being told to never take a night bus it's become pretty standard now. I have done it three times now and this is sort of a mini review.

Olongpich - PP to SR

Kings of the one star reviews, absolutely hated on Google Reviews they were perfectly fine when I took them. Bunks are too short if you are Western-sized. Paid $11 4/5


Cambolink21 Express - Poipet to SR

A little early for a night bus (8:30pm) but this is a PP bound bus. They have raised head rests that increase leg room, a big plus for us Westerners. My favorite so far. Paid $8.50 in their app. 4.5/5


Virak Buntham - SR - PP - KP

Called me at 8:30pm to tell me the departure time had changed, they're no longer doing SR to Kampot non-stop as not enough people, so bus goes to PP first. The first company I've seen that uses a 2 - 2 configuration, which makes the middle aisle a ridiculously narrow 40 cms or so. Like a coffin on wheels - not for the claustrophobic. Chassis vibrations are off the charts, a little less in the upper bunks but those have stronger lateral forces. Bottom bunk was high enough to sit up in, so at least there was that. Sleep was almost impossible. I won't be taking them again. Paid $23+ 2/5

What I found weird is that even if the bus is only 1/3 full, staff will tell you you can't sleep diagonally or take bags to your double bunk because of the other phantom person. Yeah, right.
You might get lucky when booking one of the doubles and increase your space - or sleep with a stranger (likely of the same sex only, I'd assume).

No toilets on the buses. Don't drink too much late in the day. Don't expect to get much sleep unless you're one of those comatose sleepers. The bottom bunks are right on the floor. If you are older, perhaps a bit hard to get in & out of.

Still, for a longer trip (even PP to SR is a bit short), I'd consider them again as it can save you time & (hotel stopover) money.