Eh, Usopp's intro arc has a relatively okay main battle, since they didn't drag it on too much and captain Kuro is a pretty awesome villain. Since then the battles have gotten progressively worse (save the one exception), Sanji's battle in the Arlong arc being the worst of them all.
Honestly, though, I'm not cure which is worse, the character designs or the battles. Some characters are akay, such as Zoro, Sanji and Nami, but some, like Usopp and Buggy, make me want to close my eyes and forget ever having seen them. -.-' Luffy, too, is very unimpressive for a protagonist, but at least I don't get the urge to facepalm every time he appears on the screen.
Gotta admit, though, some of the post-timeskip designs are pretty cool.