it is such a great game, really awesome gameplay, and i never get tired of it. i have had it for a while, and have played it over 6 times through and have never finished it the same way twice. you really have the choice of being a complete jerk, or a nice guy, or neutral in the dialouges, and you can choose to be on either side of a conversation. and you get to bitch slap some chick.
for one play, i'd say it is eighteen hours total gameplay, but you will play it over and over again. it is definetly worth the money, but much cheaper if you buy online.