I have flown Cambodian Angkor Air on three seperate ocassions twice between REP and KOS, and just a couple of months ago from KOS to SGN. Nothing memorable about the flights.

From the reviews though, it seems that when things go wrong for Cambodian Angkor Air, they go really wrong, and due to a lack of aircraft and crews, when a plane is out of place for weather or mechanical reasons, it is hard for the system to recover. But, in my three experiences with them, I have never had an issue.

I have flown KOS-REP, because the only way to take the bus is Sinoukville to Phnom Penh, and a second bus from Phnom Penh to Siem Reap, with a total travel time of 12 hours or so. But, I have taken the Mekong Express from Phnom Penh to Siem Reap, it took about 6 hours and was reasonably comfortable, and was so cheap it was essientially free.

If you do take the bus, take the Mekong Express, I have used them to get from Phnom Penh to Sinoukville, Saigon to Phnom Penh, and Phnom Penh to Siem Reap. They are comfortable and professional.