Yakuza 4 doesn't make any significant changes in the fundamentals of its combat, which is why I was able to hold court against crowds immediately. However, it does add some much-needed variety to both the fighting and the storyline by splitting the gameplay among four playable characters. All four have different combos and different abilities. Ex-con Taiga Saejima is slower and stronger than the other characters, and can easily throw huge barrels. Dirty cop Masayoshi Tanimura had some grappling moves the others didn't, like a punishing headlock-type grab. The homeless Shun Akiyama is a quick, agile fighter who uses high kicks and quick dashes to move from opponent to opponent. Series protagonist Kazuma Kiryu is the more "balanced" character, with average speed and strength.
In his short battle sequence, however, I noticed a new "Heat Move" (a context-sensitive finisher activated upon filling a combo meter) that allowed him to slam someone's head into the ground from a standing position -- effectively making it executable anywhere, unlike other Heat Moves that require you to be against a wall or near another feature. The facial animations have been changed this time around, so enemies' faces deform visibly when stomped on or otherwise Heat Move'd. Honestly, it falls somewhere between "too graphic" and "too cartoony," if that makes any sense. Tanimura has the deadliest Heat Move in the series, dropping dudes off the side of a building when close enough.
While walking me through the demo, Sega's Aaron Webber reiterated his comment from the PlayStation Blog that the hostess clubs, which were removed from Yakuza 3, would be present in 4. He agreed that Sega's workaround in 3, in which the hostesses just happened to be hanging out in random restaurants and asked you on dates, was a bit strange. He also said that Sega believes the uproar over the censored content in Yakuza 3 actually helped sales!
Being focused entirely on fighting, I wasn't able to experience any of the new story, or whatever new sidequest-type content is available in Tokyo's semi-fictional Kamurocho district. If it's anything like previous Yakuza games -- and there's no reason to believe otherwise -- the city will be loaded with diversions ranging from batting cages to bounty hunting, with exquisitely detailed restaurants, convenience stores, and other businesses to explore.