SCIII takes a step forwards and a step back in a few different ways...
First off, the Create a Soul aspect of the game is pretty impressive. There's a great number of clothing and armor options, and the exclusive weapons are varied enough. But you can't change the build of your character, and there are only four different voice options. Also, this is a little humorous, it's almost impossible to make an African-looking character. There just isn't the proper skin tone, unless you want an African who is VERY dark skinned.
There's plenty of replay value. The story mode, Tales of Souls, is very robust. And Chronicles of the Sword, a side game that infuses strategy elements, is brilliant. And there's plenty of minigames to play too. Tournament modes, a very robust Tutorial/Training/Practice mode...
The downfall? The AI. It is simply inhuman. On higher difficulties, the timing is absolutely perfect on these guys. They guard constantly, guard impact plenty. It's very hard to get moves in. The best way to beat the AI is often not to develop a winning strategy, but to simply spam a cheap move over and over, or use a lot of throws.
Even with this flaw, I'd recommend it. It isn't quite as polished as SCII, but the new additions make it impossible to pass up.