It's interesting you say that, because come to think of it, I played the original Okami over two separate sessions, separated by about 2 months and two games (Zelda: Twilight Princess, and Tales of the Abyss). I never fizzled at all... the only reason I put the game asside at all was because I was so stoked about getting my Wii and wanted to try it out. When I returned, it was fresh, and I still to this day put it alongside Twilight Princess, FF8+9, and Skies of Arcadia as my favorite games of all time. I tried playing through it again later on the Wii, and made it much farther than I normally do on second playthroughs, but the Wii controls just made it frusterating.
As for combat? Honestly, I have no problem with the combat in Okamiden. The series isn't exactly a shining example of revolutionary action gameplay. But Okamiden deffinitely lives up to it's predicessor. The brush strokes are far more at home with the stylus than the A-Pad or Wiimote, and incorporate themselves better into battles. The boss battles are actually a bit more interesting and challanging this time through, it isn't immediately obvious as to how to beat them, which is refreshing for a Zelda-style game.
So far, this is my favorite RPG on the DS, having not yet played Radient Historia. It easily rivals Trace Memory as my favorite DS game.