Traveler reviews for Mekong Express from Ho Chi Minh to Phnom Penh

Good service...but arrived 1 hour late almost 2 years

Everytime I go between HCMC and PP, it always takes at least 1 more hour than the estimated time. Why is that? I like Mekong express, and this time the driver let us off in the city before reaching the main office, which is far north.