1) the showdown with the crazy 88s is entirely in color. very cool to see all the action clearly.
2) in the anime with the origin of o-ren, when the girl cuts boss matsumoto, they show a shot of his body with a bit of entrails hanging out right after his blood gushed out. this was not shown in the US version.
3) when sophie was in the trunk, we see the bride cut off her other arm. in the US version, they just let you hear her scream but in the japanese one, we actually see it.
just some minor differences to think about. there's also way more extras on the japanese dvd than the crappy US version.
also, in the trailers for vol 1, we saw uma fight a bald black guy in a chinese outfit but that battle wasn't shown in either volume 1 or 2 in the theaters. so i guess we'll need to wait for the extended cut sometime down the line.