My first playthrough of Anor Londo was batshit insane, I summoned two phantoms before the staircase leading to the two Sentinels, and we just ran through the entire level. When I saw them both run up to the Archers and parry/riposte each one at the same time I was amazed. It was a 30 minute blitz through the level, grabbed every item, killed everything and smoked the boss. I was just along for the ride, it was unbelievable.
It was my first truly exhilarating co op experience in Dark Souls, but I realized I kinda ruined the true experience. So, I decided to help other people out and try to be that badass phantom in their game.
When I did my SL 4 Bandit Starter Class challenge and fought S&O with Bandit gear at SL 4, alone, I felt that I had made up for having my first playthrough be a total breeze with phantoms. I've also solo'd S&O on NG+7 difficulty and that is a similar experience.
Part of me regrets summoning help blindly before even attempting Anor Londo myself, but that experience is what made me fall in love with the online aspect of this game. Seeing how awesome you could spec out a character and being able to display your mastery of the game, all while being a huge help to someone was inspiring. Now I love being that master phantom with amazing gear and perfect stats.