Terrible. Do yourself a favor and pay a little extra to get an assured seat to your destination.
I got my tickets 3 days before and when i showed up to the station, they were late. Ok, after waiting, the bus showed up only for it to be waay OVERBOOKED. They told us to "get the next bus" which was around 6 hours later (really?).
Also the bus driver acted like it was the most normal thing in the world (probably happens a lot) and didn't apologize at all.