I am 37 hours into Okami. I did not expect it to be this long.
It's not a slog exactly, but I'm ready for it to be done.
The endgame starts when you get to the snow country.
I would say that Okami has three central acts (starting area, Imperial province, snow country), and then an endgame where you enter the giant monolith-thing after beating the pair of bosses in the ice temple place. But whatever. Semantics. Game took me a good 40-45 hours when I played it last year.
AnyHOW, still playing inFamous 2 and it's awesome. Screwing around in Gas Works, still wary about trying UGC missions. After this I'll either return to Knight of Lodis or fire up another PS3 game.