Well actually if you get 100% it's not only the ending you can watch..It's other scenes on the game that really worth the time..

But as alexholker stated above you don't have to push yourself to get 100% on your fist time..You can play it as you wish without using a guide-it's nearly impossible to get 100% without it-and you can try the second time..That's what i am currently doing..

Generally i believe that 100% really worth the effort..^_^