I've been playing okami... and I come bearing bad news.
I've beaten this game roughly 500 times on both the Wii and the PS2 as a kid, and I hadn't picked it up in years.
So I did, and this is my verdict.

The combat is AMAZING as expected, very fast, fluid, while still offering a lot of time for creativity and style to be thrown into the mix. Getting demon fangs is always a nice challenge past orochi, since you need to find the right trick for each monster, and some arent so easy to pull off.
The artstyle is well... it's okami, jesus man. It's gorgeous, moving on.
Issun.
Issun....
Good God Issun.
I hate this freaking bug. I hate him. I want to feed him to ninetails or orochi. He's the WORST videogame sidekick in any game I've ever played.
He never shuts up,he NEVER SHUTS UP. He repeats what just happened two minutes ago in the story as if we need the reminder, he makes the same jokes a million times in a row until each successive joke makes you want to give yourself a lobotomy. He never lets you solve any puzzles for yourself, as he is quite keen to interrupt you constantly to give you the answer. Never tips, just answers. I actually think Issun has more lines than the rest of the characters ingame combined.
Yeah, and people say Navi is bad. They don't know true pain. At least navi LETS you ignore her tips. Issun shoves them right in your face, with unskippable textboxes.

Overall, this game would be PERFECT without issun. The characters are really colorful, the stories solid, the environments varied, the combats fun. Everything is amazing. I just.... god dammit issun...