I'd love to know how much input Oda has with the anime staff (Pandaman, where art thou?). I appreciate all the hard work put into the anime, especially in the Philippines where they don't get paid enough.
Biggest issue with the anime is something they can't really overcome (I think it's censorship) which is the impact scars/tears in clothing from each attack, look at Gatz after being impaled!
I think I've seen it written somewhere (maybe it was here) that he doesn't actually give them that much input. One thing they do ask him about, though: when they're making a filler character with a Devil Fruit, they check to make sure that that Devil Fruit isn't going to belong to a canon character in the future (since, obviously, no repeats of Devil Fruits). And, apparently, when they were animating the flashback scenes with Shanks and Buggy all the way back in Orange Town, Oda-sensei specifically told the animators to make sure that Shanks and Buggy did not call the man who was talking to them (who would turn out to be Rayleigh) "captain." Maybe he's had other small things like that, too, but those are the ones I've heard of.