Yakuza 3 was recently reviewed by the popular Japanese gaming magazine Famitsu and it scored a 38/40. Though the magazine has come under fire as of late for some of it's more eyebrow raising reviews, a 38 is still a very good score.
Famitsu's review also revealed that the title is roughly 30 hours long. That's just for the main storyline as well, so all the karaoke singing, womanizing, golfing, tanning, and whatever other dilly dallying you have Kazuma Kiryu up to is all just bonus time tacked on to that.