Yep, I did without the guide. My sig shows my report after my first time through. Story wise it was kind of easy even on proud mode, except for a few orginization boss battles like xaldin. But some of the side missions are quite difficult, such as sephiroth and the last colliseum cup.
Also, the gummi ship and some other things will make it last atleast 80 hours if ya finish 100%