Can't do soccer offline at all (no system link and A.I can't do it).
Live is worth it though. It's the cost of buying 1 extra game a year but it's worth getting 10 or more games a year because it makes your current games oh so much more fun.
I was excited about soccer and while it is fun, the load times are killer and makes it get boring pretty quickly. Circuit racing is where the fun is at!