Soju is the Korean equivalent of Japanese saki. I do not drink but I have been told that soju is stronger than saki and has a similar taste to vodka, it has an alcohal content of 18.5 to 45%.
Everytime (6 times) I have gone out at night to eat I see Soju in small green bottles on the tables around me. Tonight over a pork, shrimp grill meal I saw upwards of 7 drunk Korean men at the same restaurant. Drinking seems to be very very common here, sort of a national pastime, among both men and women but more so among men.
Smoking is also very common, you see smokers in restaurants and all over the streets (men). The smoking problem does not seem to be as big here as it is in China but going to internet shops or restaurants filled with smokers is still a pain.