An unchanged sequel to a solid series.
The characters are nice, basically every character has been brought back, along with a couple more, plus the Star Wars characters are a very strange but welcome addition. As the author of CAD said, "We have Soul Calibur, circa 1685, everyone's fighting with swords and staves and here comes an evil cyborg from the future with a laser sword and his 800 year-old green midget nemesis."
My only beef is that The Apprentice is brutally overpowered. If he knocks me down (which isn't hard considering his moveset), he'll combo me to death and take about half my health. If I get knocked early, I always find myself saying "Oh, seems like I lost!" Other than that though, the roster is very well-rounded, and the created character feature I feel is improved from SCIII.
The story mode should be longer, I feel. I can't find myself caring about it because it feels like a tacked on joke. The tower of lost souls provides a good (if not sometimes f***ing annoying) challenge, but it gets old.
Soul Calibur IV is a good fighter and anyone that likes a good fighter but has never played a Soul Calibur should definitely pick it up, although I wouldn't blame you if you went back to SCII, but either way, it's an excellent fighter all around, it's just far too recycled mechanics-wise and stripped down story-wise for me to sing its praises.