Although the new game modes aren't everything they could be, they're full of potential and SCIII is just plain fun.
There's a gazillion of things to unlock or/and buy and money isn't hard to earn, although it WILL take a lot of time to have everything in this game.
On to the game modes, I enjoyed Tales of Souls quite a bit, although there could be more diversity to each characters' storyline. I mean, after dodging that clockwork with each character at least twice, one can only wonder how deep the game's plot really is. Don't get me wrong, it's a great mode, one of my favorites, but could've been better. Then there is Chronicle of the Swords, which seems pretty cool in the beginning but gets really old real fast. In Soul Arena, you get into mission-based fights, somewhat like a cross between Weapon Master Mode from previous games and some Super Smash Bros Melee weirdness. Sounds strange, but it's fun, although not very long.
I didn't think those other game modes as memorable (except for versus, of course), but forget all the crap people have been telling you about SCIII, if you liked the previous games, you're very likely to enjoy this one even more.